A wallet is where you store your digital assets, like crypto and NFTs - that’s the simplest way to understand it. To put it more accurately, a cryptocurrency wallet stores your public and private keys that allow you to interact with your crypto transactions on the blockchain. Crypto and NFTs are not actually stored in the wallet.
You can give out the public keys in order to receive crypto and NFTs to your wallet address. Your private key, which should never be shared, is how you gain access to your digital assets. Think of it as a key to a safety deposit box or a bank account PIN — anyone who has it can gain access.