Forces

Gravity, friction, tension and the normal force.

The everyday four

Gravity pulls everything with mass together. The normal force is a surface pushing back. Friction opposes sliding, and tension is a pull through a rope or cable.

Weight is a force in newtons; mass is in kilograms. They are not the same quantity.
Near Earth, gravity gives about 9.8 metres per second squared regardless of mass.

Free body diagrams

Draw the object as a dot and every force as an arrow from it. Most mechanics problems are solved by that drawing rather than by the algebra that follows.