Public-Private-key, Two-key, and Public-Secret-key are all names for asymmetric encryption, which involves two keys. One is your private key, which is never released to anyone; the other is your public key, which you can give to everyone in the world.

The most important thing to remember is that anything encrypted with one key can only be decrypted with the other key. For example, anything encrypted with Lee's public key can only be decrypted with Lee's private key. Anything encrypted with Lee's private key can only be decrypted with Lee's public key.