Dogs in warfare have a long history starting in ancient times. From war dogs trained in combat to their use as scouts, sentries and trackers, their uses have been varied and some continue to exist in modern military usage.
Encryption is the coding or scrambling of information so that it can only be decoded and read by someone who has the correct decoding key. Encryption is used in secure Web sites as well as other mediums of data transfer. If a third party were to intercept the information you sent via an encrypted connection, they would not be able to read it.
The encryption algorithm is the chain of calculations that determine what ways the input plain text will be transformed into the output ciphertext. In the simple example above there was only one calculation carried out, which moved each letter of the message one forward in the alphabet.