Since ".7z" is a high-compression format created by , you will need specific software to open it. What is inside this file?

: Much smaller file size than standard .zip files, making it easier to share large mod packs.

: Usually found at: C:\Program Files (x86)\Steam\steamapps\common\GarrysMod\garrysmod\addons

While the exact contents depend on where you downloaded it, a "gmods" archive typically includes: : Custom game modes or entity behaviors.