If you're learning GTA mapping, here's the actual tool list. We don't redistribute - this is editorial. For broader creator resources, gtatools.net covers GTA 6 planning tools.
Core tools
OpenIV - archive editor. CodeWalker - graphical map editor. ScriptHookV - runtime script support.
These three are the foundational layer. Almost everything else builds on them.
Authoring tools
3ds Max with the GTA plugins - the historical pro-grade authoring tool. Blender with community plugins - the free option, increasingly capable.
Both produce assets that get wired into the game via OpenIV and CodeWalker.
Supporting tools
Map Editor (in-game placement). Various converters between formats. Mod managers for clean install/uninstall.