There are three main types of encryption: steganography, cord, and cipher. Common key cryptosystems like DES and AES use the same key for both encryption and decryption, while public key cryptosystems like RSA use different keys - one public key for encoding and one private key for decoding. Transport Layer Security (TLS) is a cryptographic protocol that ensures secure communications and is often used for credit card transactions and SSL/TLS certificates provide identification on the internet.