What is video game mods?

A mod (short for "modification") is an alteration where someone, usually a player, changes some aspect (e.g. the way it looks or behaves) of a video game. Mods may range from small changes and simple tweaks to completely new games made within a video game. Games are often designed with change in mind, allowing to be modified by gamers without much difficulty.

What are compressed archive .ZIP / .RAR files?

Compressed archives contain multiple files aggregated into a single file, so that it would be easier and more convenient for a user to send them or save them on a diskspace. The most popular compressed archive format is ZIP.