I don’t have experience with it, but as I know that is a GUI helper for Wine.

A steam emulator is different. It is often just a single file, a program library that holds program code.
On windows it is a DLL file, on Linux it does not have an extension but it’s the same concept. The game loads it because it actually searches for the official version of this file, but both Linux and Windows implement the search for it so that a library file (with the expected name) besides the executable is preferred instead of whatever is installed systemwide.

Lutris on the other hand is a GUI tool to manage your “wineprefixes”, which is maybe better called wine environments. If you are familiar with python, it’s more like python’s virtual environments.
And besides basic tasks, it has a lot of additional tools to make using Wine easier.