It sounds like you're dealing with a common file structure for , a remastered version of the original game running on the Source engine.
Many total conversions or HD packs (like the Honest to God HD Pack) are distributed as zip files to be extracted into your game directory. File: Half.Life.Source.zip ...
If you're looking to create maps, you might be looking for the .fgd files or the Gameinfo.txt file found within such archives. 📂 How to Use/Install How To Enjoy Half-Life: Source WITH Mods - Steam Community It sounds like you're dealing with a common
A popular download is the Half-Life: Source Fixed mod, which addresses the many physics and lighting glitches found in the official Steam release. File: Half.Life.Source.zip ...