Screen pop-up when starting GMod

Okay so this scared the shit out of me for some reason because I thought it was going to be a screamer, but anyway when I start up GMod a screen flashes up. I’m not sure, maybe it is the Valve logo. But this only just started happening. I even deleted my GMod folder and redid it and it is still doing it. Is this normal?

A valve logo? can you confirm?