A hobby is a fairly small, very swift falcon with long, narrow wings. There are four birds called "hobby", and some others which—although termed "falcon"—are very similar. All specialise in being superb aerialists. Although they take prey on the ground if the opportunity presents itself, most prey is caught on the wing; insects are often caught by hawking, and many different birds are caught in flight, where even the quick-maneuvering swifts and swallows cannot escape a hobby.
The typical hobbies are traditionally considered a subgenus, Hypotriorchis, due to their similar morphology; they have ample amounts of dark slaty grey in their plumage; the malar area is black; and the underside usually has lengthwise black streaks. The tails are all-dark or have only slight bands.