Huffman compression belongs into a family of algorithms
with a variable codeword length. That means that 
individual symbols (characters in a text file for
instance) are replaced by bit sequences that have a
distinct length. So symbols that occur a lot in a file
are given a short sequence while other that are used
seldom get a longer bit sequence. Huffman compression
works best with ascii files. The algorithm is about
50 years old and is used in a variety of formats such
as GIF, JPEG and PKZIP.

