VectorA:Cross(VectorB) returns the vector C/returns a vector that is perpendicular to Vector A and B. You might want to use this function if you want to fire a ray to the right of your Roblox character
The dot product basically returns 3 whole numbers, 1, 0 and -1. It returns 1 if 2 vectors are facing in the same direction. It returns 0 if 2 vectors form a right angle. It returns -1 if 2 vectors are facing the opposite direction. You might want to use this function if you want to let a player fight a monster if its in front of your character or letting a player interact with an NPC if its facing towards it.