Ether (ETH) is a cryptocurrency used on the Ethereum network. It is used to pay for transactions and services on the Ethereum network, such as smart contracts and decentralized applications (dApps). Ether is also used as a form of digital currency, and can be bought and sold on cryptocurrency exchanges.
For example, if you wanted to use a dApp on the Ethereum network, you would need to pay for it in Ether. The amount of Ether you need to pay depends on the complexity of the dApp and the amount of computing power it requires.