You will never find a better article than this on css tricks, where all the good things on gzipping are explained. There's also a comparative between gzip and minification and why you should use both or one, or none (both, the answer always is both ;)). In a nutshell, gzip return to the browser a file version with "pointers" to the first instance of a strings; so if you have many divs, instead of sending the textual <div> it will return a reference to the first instance, this reduce significantly the file size that the end user receives. I hope you understand the concept and the benefits of gziping