When jumping into the world of crypto there are three basic that are used when referring to a blockchain and its native cryptocurrency, and for the Ethereum blockchain these are "Ethereum", "ether", and "ETH". While directly related to each other, there are subtle differences between them, and understanding what a blockchain is helps with their context.
A blockchain is a decentralized network operated by independent individuals and businesses across the world, each of which is hosting a copy of the network's transaction history. Most blockchains are designed around pseudonymous s, or "crypto wallets", that can hold a single cryptocurrency. The blockchain's "native" cryptocurrency is used for paying network fees, while all other cryptocurrencies are programs running on the blockchain, and are not tracked the same way as the native token. Thus, when talking about a blockchain, there are for the blockchain network, its native cryptocurrency, and the cryptocurrency's ticker symbol used by crypto exchanges.
As the Ethereum Foundation writes on Ethereum's official website, Ethereum is a programmable blockchain that can be used to write small programs, called "smart contracts". Ethereum's native cryptocurrency, ether, has the ticker symbol "ETH", and is required for using smart contracts. ETH can be purchased on any cryptocurrency exchange, and then withdrawn to a personal Ethereum wallet. Many people who buy ETH don't know that it is short for "ether", and will use "Ethereum" to refer to ETH/ether. "Ether" is more commonly used by blockchain developers who build on Ethereum, but they also use "ETH" more than "ether". For most contexts, the only that are needed are "Ethereum" (the network) and "ETH" (the cryptocurrency), while "Ethereum" can be used in place of "ether".
Ethereum Hosts Smart Contracts, ETH Pays For Them
The real value of Ethereum is its smart contracts. Smart contracts can create assets such as cryptocurrencies and DAOs, the Web3 communities used for governance, among other utility purposes and niches. To interact with these smart contracts, a crypto wallet must contain an appropriate amount of ETH to pay for the network fee involved in updating the blockchain's data. Part of this fee is given to the participants running the network, which incentivizes participation and thus encourages decentralization of the network.
Ethereum is often the testing ground for new ideas in blockchain, as its smart contracts are responsible for the 15,000+ cryptocurrencies in existence, the NFT craze, the Decentralized Finance (DeFi) industry, the Play-to-Earn (P2E) gaming industry, the hundreds of millions of dollars lost in scams, hacks, and poorly tested code, Web 3.0 (the blockchain powered internet). Because Ethereum was the first smart contract blockchain built in a relatively short time, Ethereum suffers from a design that is quickly bottlenecked by network congestion, which causes ETH fees to skyrocket. These fees can range from $4 to $50 for most actions, but during high activity can go into the hundreds, making Ethereum unusable for most people. While Ethereum is slowly upgrading to a better system, this process has taken years, and it will be some time before the transaction fees become reasonable for use in applications intended for large-scale audiences. To fill the ongoing demand for cheap smart contracts, there exists Ethereum scaling solutions like Polygon and alternative smart contract blockchains like Solana.
In summary, Ethereum is a blockchain network that runs smart contracts, ether is the cryptocurrency paid to use Ethereum smart contracts, and cryptocurrency exchanges sell ether under the ticker symbol ETH. When referring to ether, most people will vocally use "Ethereum" (i.e. "I want to buy more Ethereum."), and in writing will use "ETH". Developers commonly refer to ether by its actual name, while everyone else just uses "Ethereum".
Source: Ethereum