Wallets are applications that let you interact with your Ethereum account. Think of it like an internet banking app – without the bank. Your wallet lets you read your balance, receive transactions and send transactions.
You need a wallet to send funds and manage your ETH.
Your wallet is only a tool for managing your Ethereum account. That means you can swap wallet providers at any time. Many wallets also let you manage several Ethereum accounts from one application.
That's because wallets don't have custody of your funds, you do. They're just a tool for managing what's really yours.