A machine is any device that does work. Machines make our lives a bit easier because they reduce the amount of energy, power, and time we need to get one thing done by magnifying our input force.

A machine can increase the magnitude, or the distance of a force but not both at the same time.

Machines come in many sizes, shapes, and forms. Some machines are simple in their makeup and use, while others are very complex. For example, a spade is a machine (a simple machine), and a space shuttle is a machine too (a complex machine).
For this lesson, we shall be looking at simple machines.

Consider the illustration below:

To bring the load (wagon with a mound of dirt in it) to the lower surface, a person has to carry that carefully. That is a lot of muscle work. To make that a bit easy, we can just put a ramp there and give the wagon a little push — right? Yes, and then the load will slide down on its own.
In the example above, we have used a simple trick of a simple machine to bring down that load of dirt — easy peasy!

Here is another scenario:
A bulldozer at work! Take note of the simple machine units (levers, wheel and axle, wedge) that are combined to build a complex machine.

To push a mound of dirt on a piece of land, it can take a person with a shovel a lot of time and energy to do so. However, one person with a complex machine can do that work in no time. Here, the complex machine, which is a complex combination of simple machine units, use mechanical energy and electrical energy to do that job. It is not the same as a simple machine. This bulldozer is an example of a compound or complex machine.

Now let us take a look at some simple machines types.