How do you use Velocity?

Velocity is telling the brick in the physics engine where to move every frame, and how far. XYZ are Left/Right, Up/Down, and Forward/Back. The way it tells which way it should go in either XYZ coord is if the value is positive or negative. Velocity can also be used; due to how physics in roblox work; to make "treadmills" by setting a velocity to a brick while it's anchored. Whenever a player stands ontop of that brick, it will add that velocity to the player. It can also be used to make trampolines.