Meaning – The process of eliminating gaps, empty fields, redundancies, and unnecessary data to shorten the length of records or blocks, is known as compression. This process if used predominantly, to reduce the size of a file that you wish to share, but are unable to do so, due to file size limitations.
Compression of files can either be lossy or lossless. If the former method has been adopted for compressing a file, then the bits that have been removed in the process, cannot be recovered. On the flip side, the use of a loses method of compression, will not reduce the size of the file as much as a lossy method would.
In the context of encryption, the process of compression is the process of reducing the bits required to represent the contents of a message.
Example of usage – “The programmer decided to use a lossless method of compression for his files, as he wanted the option of restoring them back to their original sizes if required.”