Final answer:
A simple machine is a device that can multiply or augment a force that we apply, while a compound/complex machine is a combination of two or more simple machines.
Step-by-step explanation:
A simple machine is a device that can be used to multiply or augment a force that we apply, such as levers, gears, pulleys, wedges, and screws. They can reduce the input force needed to perform a job and have a mechanical advantage.
A compound/complex machine is a combination of two or more simple machines. For example, bicycles include wheel and axles, levers, screws, and pulleys. Cars and other vehicles are combinations of many machines.