Gzip

Gzip is GNU Zip, an open source (yay!) form of file compression that is used in order to reduce file size (archive – like zip) and also to allow for faster file transfer.

Most modern browsers can render Gzipped content easily – making the time spent receiving the files much reduced in setups which Gzip HTML, JS and CSS files by default.

Gzip can compress text based files really efficiently. Images less so, as files like JPG are already to a large degree compressed.