The chorus: A repeated section, often the most memorable melody in the song. Michael Jackson's "Billie Jean" uses two verses before its chorus. The chorus uses repetitive lyrics stating the speaker's summary of the action.
The bridge: A change of pace featured later on in the song, often following a chorus. If a fresh idea happens right before a chorus, it may be called a pre-chorus. "Billie Jean" uses a pre-chorus after the verse and before the chorus. This is used to build up the tension before letting loose in the song's melodic hook.