A very simple form, always in 3/4 meter, with two phrases, each repeated, in the minuet; then the trio, also of two phrases, each repeated; then a return, or da capo, to the minuet, skipping the repeats:
A minuet often comes as the third movement of a four-movement form like a symphony or string quartet. A sonata-imbued design is often built into the form by recapitulating the first phrase in the second (xyx, etc.); this makes the second sections nearly twice as long as the first.
Da capo means "from the top" ("from the head"): the music is not usually rewritten out, and the musicians return to the top and, by convention, skip the repeat signs.
The center section is called trio from its origins in Baroque dance: two treble instruments and a bass instrument would spell the main ensemble from time to time. Trios typically, therefore, are in some sort of reduced texture, often gentler and more lyrical than the minuet that surrounds them.