Each cryptocurrency wallet has a public key and a private key.
The public key allows you to receive cryptocurrencies from anyone who has the address of your public key. Because the public key is often very long you normally use a hashed version which we better know as a "wallet address". The wallet address is a long string of alphanumeric characters and is the address you use when buying and selling cryptocurrencies or transacting between wallets.
The private key on the other hand is a key that you should never share with anyone. The private key is used to unlock your cryptocurrencies sent to the public key and proves that you are the owner of the wallet and the cryptocurrencies within it. Anyone with the private key can get access to your cryptocurrencies which is why you should never share the private key with anyone.