The way that Blockchain transactions are sent involves a secure sign off process, also known as Cryptography. For each individual, the Public and Private Keys are generated as a pair and are linked mathematically.
Your Public Key, which you can also think of as your public address, is an alphanumeric number that is used when people want to send you digital currency or other transaction data. When a transaction is sent to a Public Key address, it is encrypted, similar to how password and credit card information is stored on websites, like Amazon. You should share your Public Keys with as many people as possible because they might send you digital currency.
Your Private Key, which you can also think of your private address, is also an alphanumeric number that is used to unlock data and transactions sent to your Public Key address. Since your Public and Private Keys are linked, only your Private Key has the ability to unlock what is sent to your Public Key address. Therefore, it is of the utmost importance that you never share your Private Key and that you keep it safe and secure.