#2
They're virtually the same. They just refer to the section between the second chorus and third chorus. For more specific definitions...

Interlude: A short, usually instrumental section that links two longer parts of the song

Break: Essentially the same as an interlude, though I see a break as containing fancy guitar work

Breakdown: This section is typically different than the rest of the song. If the song is heavy, this section will be REALLY heavy or more melodic/acoustic based. I would consider the slower section of Maiden's 2 Minutes To Midnight a breakdown, though in metalcore, the breakdown is often the heaviest section of the song.

Bridge: The standard structure of a rock song is Verse-Chorus-Verse-Chorus-Interlude-Chorus.

Those are hardly rules, though.