Simple machines can include common tools like bottle openers, axes, or even door handles.
On the other hand they can be part of complex devices like automobiles and airplanes. In fact, people just don't realize how common the simple machines are. Every time you open a door, go upstairs, use scissors, and even move your limbs, you are utilizing simple machines. Without these machines we would all still be living in caves. Simple machines are useful because they can make a physical job easier by changing the magnitude or the direction of the force exerted to do work.