As a noun, 区 names administrative subdivisions (海淀区), residential compounds (小区), and zones of any kind (商业区 commercial district, 景区 scenic area). As a verb it means to distinguish or differentiate, seen in 区别 and 区分.
register
Rare second reading: 区 is a surname (first tone). Almost all modern bearers of this surname write it as 欧 instead, so you will hardly ever meet 区 in the wild. In every common word, place name, and compound below, 区 is read qū.
Components
ideograph
区qū
area; district
Heavily simplified from 區 (three 口 boxes stacked inside a 匚 — subdivisions within one boundary, the picture of an administrative region). The 1956 reform collapsed the three boxes into a single 乂 inside the frame. Indexed under Kangxi #23 匸 (hiding-frame) by tradition via the surrounding three-stroke shell.
Filed under radical 匸 (xì, #23) by convention. 匸 is not a separate component in 区, so no strokes are highlighted.