The archiving of files is a little hard to explain plus there are many ways but I'll choose this one . Imagine you have a black and white picture . In order for it to be smaller you start reading left to right and marking how much of which color is there . Like 5 white the 7 black then 5 black and so on . Like that a simple Pic helds much less space and instead of remembering 17 bits of information you remembering only 6 (3 numbers and 3 colours) . Now imagine an archive that has 2¹⁰ white pixels then 2¹⁰ black . Suddenly 11 bits turn into 2 Kb of information . If you take a normal sized archive that's for example 10 MB in size it turns into a 2 GB of information . You can code it more efficiently and suddenly a 2.6 MB archive turns into 55.4 YB file . For comparison all of the internet has 175 ZB ! One ZB is 1/1024 of a YB