Newton's first law of motion - law of inertia . An object with no net force on it travels at constant speed in a straight line. Special case, if the speed is zero, it stays zero. There is acceleration whenever the direction of velocity changes.
Weight is a force on a mass due to gravity.
Weight is measured in newtons, while mass is in kg. The mass on the Moon stays the same as on Earth, but the weight is about one sixth. For example a 120 lb person on Earth has a mass of 55 kg. Friction force always is in opposite direction of motion. Static friction will have a maximum value that is more than sliding friction.