When someone sends you cryptocurrencies over the Blockchain, they are actually sending them to a hashed version of what’s known as the “Public Key”. This generates or can be synonymous with the address you will see in your wallet or exchange that allows you to send and receive Cryptocurrencies with other peers.
There is another key which is hidden from them, that is known as the “Private Key.” The “Private Key” is what proves you are the owner of Bitcoin and allows you to generate your balance or restore your wallet on any device at any time. You can know your own Private Key, and everyone else on the Blockchain knows their own Private Key, but the Private Key should not be shared with anyone!
Think of a “public key”/“wallet address” as your username or email address. You can give this to other people to find and communicate with you, just like you can give your public key in order to send and receive coins.
Think of a “private key” as your password or social security number. If you give this to anyone they have the ability to pretend to be you and have access to your assets.