Over the past two decades, work on ultracold atomic gases has exploded, driven chiefly by advances in experimental techniques. I shall give a brief history of this field, laying stress on physical ideas and basic concepts. This will be followed by a discussion of length and energy scales and some of the important tools in the field. I shall attempt to highlight some of the reasons for the success of this field and will also consider the synergy between the physics of ultracold gases and other subfields of physics.
