How do I make a raycast go from the cameras angle?

If I was to make a player constantly face the way my camera is facing using a raycast, what would I need to do?

I know raycasts are points that go from a start to an end, so that's easy to comprehend but when it comes to figuring out how to actually shoot a raycast going from the cameras angle I am a bit confused. I need help, could someone explain this please?