Cocos - is our GUI tool that helps create new projects and manage projects. The future of this project is unknown. Cocos GUI never supported VS 2015.
cocos - is also available from the command-line and does most of what the GUI tool does, but it isn’t helpful with project management like the GUI tool was. When you run cocos new there should be a VS project created. If you are running v3.13.1 then have a look here specifically at the post by @IanHu
Cocos Studio - this was our layout and scene creation tool. It is EOL’d
Code IDE - this was our JavasScript/LUA IDE. It is EOL’d
Cocos Creator is our new unified game development environment. It supports JavaScript. Lua and C++ are coming. There is this thread where @ricardo is providing updates on his progress.