NGSS
Compound machine
A machine made of two or more simple machines. Compound machine. A compound machine is like a toy that uses several parts, like levers and wheels, to help us do things more easily.
Machine
A device that makes work easier by changing the size or direction or both of a force. Machine. A machine is something that helps us do things more easily, like lifting a heavy box.
Output force
The force exerted by a machine. Output force. Output force is the push or pull a machine gives to move or lift something.
Pulley explained in an easy to understand way.
Wheel and axle explained in an easy to understand way.