Humans have been building Mechanical systems for thousands of years. Over time, several basic elements were created, and are now referred to as "simple machines". Simple Machines are the very basic building blocks of mechanical operation, and provide the user with a form of mechanical advantage. Simple machines make working and living easier, and have allowed for continual human development throughout history.
6 different simple machines:
the lever
the wheel and axle
the pulley
the inclined plane
the wedge
and the screw.
These 6 elements form the basis for complex machinery even today. The 6 machines can be divided into 2 categories based on their operation: machines that require an equilibrium of torque, and those that require an equilibrium of vector forces.