Powerful rockets are used to send artificial satellites into space. If the launching speed of the rocket is too low the satellite will fall back onto Earth because the gravitational attraction exerted by the Earth on the satellite would be too high for the satellite to overcome. The same happens to a rock thrown by a person from the Earth's surface, if falls back onto the Earth. On the other hand, if the launching speed is too high, the satellite will not be confined by the Earth's gravity and it will escape to outer space. You can imagine that placing a satellite in a particular orbit requires some accurate calculations and careful work.
Artificial satellites serve multiple purposes nowadays.
The orbits of some satellites are synchronized with the rotation of the Earth. If their speed matches exactly the speed of rotation of the Earth, they look as if they are stationary on the sky and they are therefore called geostationary satellites. If the relative speeds are not the same, the satellites look to us like the Moon, rising and setting, sometimes even several times a day. We need some form of communication with the satellites to send them commands and to retrieve the information that they acquired while orbiting the Earth. Although they have different means to communicate this information, the basic alphabet used consists of radio waves , which are exactly the same type of waves used to broadcast television and radio programs.