X-ray Astronomy for non (X-ray) astronomers

Observations of X-rays coming from outside the solar system were pioneered in 1962 by Riccardo Giacconi and colleagues. From that very day, it became evident that X-rays would reveal a very different Universe to that shown by optical or radio telescopes. Indeed, X-rays are typically produced in the environment of black holes, or where the ambient temperature exceeds millions of degrees. X-ray telescopes (which, for good reason, are in orbit) and their instruments look radically different to those on gthe ground. What do we learn by observing the sky in X-rays and how do we do it?