The Four Rules of Key Selection
Encrypt
To send a confidential message to someone, encrypt with their PUBLIC key. Only their private key can reverse it.
Decrypt
To read a confidential message sent to you, decrypt with your own PRIVATE key.
Sign
To sign a message as yourself, encrypt the hash with your own PRIVATE key. Only you have it.
Verify
To verify a signature is from someone, decrypt it with their PUBLIC key. Match the hashes to confirm.