It allows games to run without the Steam client active.

The file refers to a specific modified version of the game Portal with RTX , which is a free DLC that adds ray tracing to the original 2007 title . 1. The "RTX" Component

If you own Portal on Steam, you can download the official Portal with RTX DLC for free from the Steam Store. This ensures you have the most secure, stable, and up-to-date version of the game.

It can bypass Steam’s online requirements for local multiplayer.