A radio telescope is a type of antenna, like a huge satellite television dish. It is used for radio astronomy. Stars shine and the light can be seen with an ordinary telescope, but they also give off radio waves. Scientists with radio telescopes receive these radio waves and use computers to learn about the stars. Other things like black holes also give off radio waves and radio telescopes are useful for learning about them too.
The dish is sometimes constructed of a conductive wire mesh whose openings are smaller than a wavelength. The information received by several radio telescopes in different places can be combined. This gives similar results to having a single dish as big as the distance between the telescopes. It can receive very faint signals, and see more details. The biggest telescope is a virtual radio telescope almost as big as the Earth, called the Event Horizon Telescope.