The Data Encryption Standard (DES) is an algorithm used for encrypting computer data. It was developed in the 1970s by IBM with the support of the National Security Agency for the National Institute of Standards and Technology (called the National Bureau of Standards back then). DES is a form of private key encryption (PKE), which uses a special code called a key to encrypt and decrypt a message. DES uses a 56-bit key that's the result of using eight bytes of key where every eighth bit is a parity bit, providing a total of 56 bits of effective key.
DES was originally designed for the U.S. government to protect data and transmissions, and it still is. Once thought to be too easy to break, it has proven itself over and over again in the past decades. With today's computing power, a brute force search can be done for the one 56-bit key that works, if you have lots of time (i.e., many days of supercomputing power).
While DES has been broken, it's still used. Typically, the algorithm comes in the 3DES or triple DES format, which means to encrypt the data you use three keys and repeat the DES three times. The result is a practically unbreakable code.
DES is one of the oldest PKE codes, and it's still widely used in ATM machines, point-of-sale terminals, and other systems. Though newer encryption codes are available, DES lives on in the 3DES form and still does a very effective job. And, it can be easily implemented in hardware or software.