Data Compression
Data compression is the act and process of encoding information using fewer bytes. This can be important if you run a website or send a lot of documents via email (or other electronic means.)
Compression relies on the notion that the data is superfluous or redundant. A compressor reduces the size of a file by deciding which data is more frequently used and assigns it less bytes than to lesser used data. An example of a data compressor is a Zip file format which on top of compressing acts as an archive and stores many course files in a single destination.
Compression is used to help reduce the consumption of resources such as transmission bandwidth - and that can affect the size of hosting you need for your website.