Encryption refers to converting data into a different form so that it cannot be understood by anyone except the intended recipient.
The information is fed through an algorithm, which scrambles the basic text to a form that is indecipherable. The recipient also possesses the algorithm, often called the encryption key, and hence can decrypt the information to a readable form.
The key to encryption is that while an eavesdropper may be able to intercept a communication, they will only be able to access gibberish without the key.
The concept has taken on new importance in the digital age, in which cryptographers use the techniques to secure computer systems and digital communications. This includes both stored data and data travelling across communication channels.