The choker shot is very similar to the extreme closeup (ECU), and the two terms are often used interchangeably. A typical choker shows the subject's face from just above the eyebrows to just below the mouth, as pictured left. Other common variations are illustrated below.
As with all shots that are this tight (i.e. zoomed in this much), you really need a good reason to use it. Chokers should be used judiciously as not everyone will be flattered in such a revealing view.