On X-ray telescopes in general and the Athena optics in particular

The optical design of the most common type of X-ray telescopes is reviewed in this contribution and the imaging properties of these are discussed. Then the newest mostly European large mission, Athena, is presented and some of the most important properties imaging-wise are reviewed. Finally the science program for Athena is described where the emphasis is on the cosmic web and the population of AGNs.