Satellites and Centripetal force

A satellite is any object that travels around another object in space.

An artificial satellite is a device launched into orbit around Earth. Artificial satellites are designed for many purposes. They are used in space research, communications, military intelligence, weather analysis, and geographical surveys.

Source: Wikipedia

Any force that causes an object to move in a circle is called a centripetal force ("center seeking").

An object traveling in a circle is accelerating because it is constantly changing direction. For a satellite the centripetal force is the gravitational force that pulls the satellite toward the center of the Earth.

Source: Science for Kids 

Satellites in orbit around Earth continually fall toward Earth, but because Earth is curved they travel around it. In other words, a satellite is a projectile that falls around Earth rather than into it. A satellite does not need fuel because it continues to move ahead thanks to its inertia. At the same time, gravity continuously changes the satellite's direction.
The speed with which an object must be thrown in order to orbit Earth turns out to be about 7,900m/s!