Tutorial for Forks

Hello, newbie here going through the lessons here on Chess.com. I'm up to the Fork section and I am a little confused. Does the image below invoke check? The session says this is a wrong move and then takes my knight with the bishop. Apologies if I am missing something obvious.

Qg4+ forks the rook and the king.

But does the knight not do the same thing, or am I missing something?

It could, but the bishop would just capture it for free.

but wouldn't the king have to move first? 

No. They can capture the knight with the bishop to get out of check.

Ahh, of course. Thank you, still learning

You're welcome.

You can ask me any questions you might have about chess.

Much appreciated thanks!

It's good to remember that there are three ways to deal with a check: 1.Move the king. 2.Capture the checking piece. 3. Block the check (which is impossible if the knight is giving check)