How would I go about doing this? (player looking at a specific object)

Me and a friend are making a game and (as of now) there isn't any other place I can find to help with this.

I already attempted to make it myself but I can't really figure any of out.

I am trying to make it so if a player is looking at a specific object, something happens. If I am correct, I am pretty sure this has something to do with camera properties? (camera.focus?)

I hope someone is willing to help me figure this out.