A Public/Private Key Pair consists of 2 keys— 1 Public & 1 Private

Encrypt with either the public or private and try to decrypt with the same key.
It doesn't happen!
You must use the other key to decrypt.

That's the big, big benefit —openly share your public key; public key encryptions stay secure.
Only the corresponding private key can decrypt it!

This also enables digital signing; private key encryptions prove she used her private key.

Try it here and learn more in the next section→ Alice & Bob.