Over the last decade, there has been a dramatic increase in the number of
astronomical instruments that use adaptive optics. In the era of extremely
large telescopes, adaptive optics will become even more important. But what
is adaptive optics and how is it used? In this introductory talk, I will describe
what adaptive optics is and how it works. I will also define some commonly used
terms, such as the Strehl ratio, anisoplanatism, and the cone effect. During
the talk I will emphasise not only the strengths of AO, but also some of its limitations
and, at the end of the talk, I will describe how future instruments and telescopes
will overcome some of these limitations.
