Bitcoin, Ethereum, and Stablecoins
Bitcoin is digital scarcity, Ethereum is a programmable platform, and stablecoins try not to move; learn these three and most of the market makes sense.
- Fixed supply, only 21 million will ever exist
- New coins halve about every four years
- Treated as digital gold, scarce and hard to debase
- Smart contracts run on their own, no middleman
- Every action costs a fee called gas
- ERC-20 is the shared standard for new tokens
- Aims to stay close to one dollar
- Park value without leaving crypto
- Smooths payments and pricing
Look at the three panels above before reading on. Thousands of cryptocurrencies exist, and the sheer number is the first thing that scares a beginner off. Here is the good news: you do not need to learn thousands of them. Almost everything on the market fits into those three buckets, and once you can tell them apart the noise settles down. Bitcoin is about digital scarcity, something there is a fixed amount of. Ethereum is a platform other things get built on top of. And stablecoins are crypto that deliberately tries to sit still. Get these three straight and the rest of the market stops looking like an alphabet soup.
Bitcoin: digital scarcity
Bitcoin's headline feature is that there will only ever be a fixed amount of it. The rules cap the total supply at 21 million coins, and no authority (no company, no government, no founder) can change that number. That fixed ceiling is the whole point.
New coins do not appear all at once. They enter circulation as the reward miners earn for adding blocks to the chain (Module 2). But that reward is cut in half at regular intervals, every 210,000 blocks, which works out to roughly once every four years. This event is called "the halving". The reward started at 50 coins per block, dropped to 25, then to 12.5, and keeps stepping down toward zero.
Because the supply is capped and new issuance keeps shrinking on a published, predictable schedule, many people treat Bitcoin as "digital gold": something whose main job is to be scarce and hard to debase, a store of value rather than a fast way to pay for coffee. Whether it lives up to that is still debated, but the design is a direct answer to the inflation problem from Module 1. No one can print more of it to dilute what you hold.
Ethereum: a programmable platform
Ethereum aims at something different. Where Bitcoin is deliberately simple and does one thing well, Ethereum is a general-purpose platform for building on.
The key idea is the "smart contract": a small self-executing program stored on the blockchain that runs automatically when its conditions are met, with no middleman to enforce the deal. Think of it as an agreement that carries out itself. This lets developers build applications (lending, trading, games, digital collectibles) that all run on the same shared ledger.
Running these programs is not free. Every action on Ethereum costs a fee called "gas", which pays the network for the computing power it uses. When the network is busy, gas fees go up. Ethereum also popularised a common recipe for creating new tokens, called the ERC-20 standard. It is a shared set of rules so that any new token behaves predictably, which is why wallets and exchanges can support thousands of different tokens without building custom plumbing for each one. That is a big reason Ethereum gets described as the platform the rest of the ecosystem is built on.
Stablecoins: crypto that tries not to move
Bitcoin and most tokens are volatile. Their prices swing hard. Stablecoins are the deliberate opposite. A stablecoin is a cryptocurrency designed to hold a steady value against a reference asset, most often the US dollar, so that one unit stays close to one dollar.
They exist for very practical reasons. They let you park value in dollars without leaving the crypto system, which is handy when you want out of a jumpy position but not all the way back to your bank. And they make payments and trading smoother, because both sides can price things in a steady unit instead of a moving target.
One honest warning: stablecoins are "not necessarily stable". The name describes a goal, not a guarantee. Different stablecoins hold their value in different ways, and some have failed and broken their peg in the past. Treat the steadiness as a design aim to be checked, not a promise.
Coins vs tokens: a distinction worth knowing
Beginners mix up "coin" and "token" constantly, but the difference is simple once it clicks.
A coin is the native currency of its own blockchain. Bitcoin (BTC) is the coin of the Bitcoin network. Ether (ETH) is the coin of Ethereum. A coin is built into its chain and is what you use to pay that chain's fees.
A token is issued on top of an existing chain, using that chain's rules, without having a blockchain of its own. Most stablecoins and most smaller projects are tokens. An ERC-20 token, for example, lives on Ethereum, relies on Ethereum's security, and pays its fees in ETH.
The rule of thumb: if it pays the network's fees and helps secure the chain, it is a coin. If it lives on someone else's chain, it is a token.
The maths behind the 21 million cap
The 21 million ceiling is not an arbitrary round number that someone wrote down. It falls out of the halving schedule. Each halving era is 210,000 blocks long, and each era pays half the reward of the one before:
- Era 1: 50 coins x 210,000 blocks = 10,500,000 coins
- Era 2: 25 coins x 210,000 blocks = 5,250,000 coins
- Era 3: 12.5 coins x 210,000 blocks = 2,625,000 coins
Add up just those first three eras and you already have 18,375,000 coins, about 87.5% of the eventual total. Because each era adds half of the previous one, the amounts keep shrinking and the running sum creeps toward 21,000,000 without ever going past it. That is the elegant part: the schedule is fixed and public, so anyone can work out roughly how many coins will exist far into the future, and no one can quietly issue more.
How stablecoins try to hold their peg
Not all stablecoins keep their value the same way, and the method matters a lot for how trustworthy the peg is. The three broad approaches:
- Fiat-backed: the issuer holds real dollars (or short-term dollar assets) in reserve, ideally one dollar in the bank for every one coin issued. The peg is only as good as those reserves and how honestly they are audited.
- Crypto-backed (over-collateralised): the coin is backed by other crypto locked up as collateral, and because that collateral is itself volatile, the system deliberately holds more than one dollar of it per coin as a buffer.
- Algorithmic: the coin tries to hold its price using code and market incentives rather than reserves. This is the most experimental design, and it is the category where some of the most famous peg failures have happened.
The takeaway for a beginner: "stablecoin" is a label, not a promise. Knowing which of these three backs a given coin tells you how much you are really trusting, and who you are trusting.
Why Ethereum needs 'gas' at all
Gas can feel like an annoying extra fee until you see what it is for. Ethereum runs programs (smart contracts) on thousands of computers at once. Someone has to pay for all that computing, and there has to be a brake on people clogging the network with endless or wasteful code.
Gas solves both problems. Every operation a contract performs has a small cost, and you pay for exactly the work your transaction uses. A simple transfer is cheap; a complicated app interaction costs more. When lots of people want to transact at the same time, they effectively bid for limited space, so fees rise during busy periods and fall when things are quiet. It is a pricing system that keeps the shared computer from being flooded, and it is why the same action can cost very different amounts at different times of day.
Quick knowledge check
What is Bitcoin's maximum supply, and how often does the block reward halve? There will only ever be 21 million coins. The reward paid to miners halves every 210,000 blocks, which comes out to roughly once every four years. Both numbers are fixed by the rules and cannot be changed by any authority.
What is a smart contract, and which platform is best known for them? A smart contract is a self-executing program stored on the blockchain that runs automatically when its conditions are met, with no middleman needed to enforce it. Ethereum is the best-known platform for building them.
What is the difference between a coin and a token? A coin is native to its own blockchain and pays that chain's fees, like BTC on Bitcoin or ETH on Ethereum. A token is issued on top of an existing chain using that chain's rules (for example an ERC-20 token on Ethereum) and does not have a blockchain of its own.
Sources
- Bitcoin Developer Reference, "Block Chain", the 21 million supply cap, the block reward, and the halving every 210,000 blocks.
- ethereum.org, "Introduction to smart contracts", what a smart contract is and how self-executing programs run on the chain.
- ethereum.org, "Gas and fees", why Ethereum charges gas and why fees rise when the network is busy.
- ethereum.org, "ERC-20 Token Standard", the common rule set that lets fungible tokens behave predictably across wallets and apps.
- US Federal Reserve, FEDS Notes, "The stable in stablecoins", stablecoins aim to hold a steady value against a reference asset and are not necessarily stable; some have failed.