The nexus websites are a modders marketplace you could say. Though its quite contrary to a market since the mods are free. Its a place where you can get mods for various games.
All games from Bethesda and other games too will have their respective nexus website with link to mods.
E.g
Witcher games:
The Witcher Nexus - mods and community
The Witcher 2 Nexus - mods and community
My mod page
Witcher 2 EE Saves- The path of your choice at The Witcher 2 Nexus - mods and community
Tw1 is a gem for its storytelling more than its combat
Even I played tw1 after tw2 but enjoyed certain aspects of tw1 better and ended up spending more time on tw1.
Have bragging rights : playtime of 300 hours on tw1 and tw2 each
Sad there was no galaxy back then for game time tracking.