Well I'll tell you. Encryption is the act of modifying data so that only the person who encrypts it can decrypt it. That is, the data you are encrypting is essentially locked with a digital key in such a way that only that key can unlock it. What I described would be called a symmetric encryption algorithm, where there is only one key used to both encrypt and decrypt data. The most notable symmetric key algorithms are AES, 3DES, and blowfish. There are also asymmetric algorithms where key pairs are generated in such a way that when you encrypt something with one key, it can only be decrypted with its pair (a different key). These keys are refered to as public and private keys. The most popular asymmetric algorithm in use today is RSA, but could soon be replaced by eliptic curve cryptography. But enough of this jibery joo, that's what wikipedia is for, lets check out some programs.