VERSES: the part of the song that tells the story. The verses explain what is going in the song or develops the "plot", if the song has a plot. The vast majority of popular songs with lyrics contain either 2 or 3 verses. Another way to tell the verses is that the words change, but the melody may be the same or very similar, just song to different words in verse 2 compared to verse 1, for example.
REFRAIN / CHORUS: contains the song's theme & usually its title. By far, a song's refrain (or chorus, which means the same thing) is the most important part of the song, and almost always repeated the most. The chorus occurs on average three to six times in a song. Sometimes, many more. In some songs, the final minute or so of the song simply repeats the chorus over and over, thus emphasizing its importance. This also helps makes a song familiar and one you can learn to sing along with quite quickly.
Some songs contain a PRE-CHORUS: a unique set of lyrics which always lead directly and immediately into the chorus. The pre-chorus helps build momentum and anticipation to the chorus of the song. NOT part of the verses and NOT part of the chorus, the Pre-Chorus is heard right before the chorus of a song.
BRIDGE An entirely different passage of a song that "bridges" or follows a few verses of a song and leads to the song's chorus. A song's bridge has a completely different melody and "feel" from the rest of the song, appearing only once (in the 2nd half of the song), and often leads back to the chorus. Some bridges contain lyrics, some are instrumental only.
BREAKDOWN: A breakdown occurs often, in many songs of all genres. It's called a breakdown because it feels like the whole song is falling apart, or "breaking down"!
The breakdown of a song happens when almost all the instruments stop and you only hear one or two instruments (typically just drums or just a bass guitar) keeping the rhythm going, after a short while, the song provides lots of relief and impact by then returning to the chorus, which usually repeats a few times before the song ends.
If a song has a breakdown at all (only about 20% of songs have a breakdown, but enough to bring up the term in this lesson) it will always occur in the last third of a song, often just a minute or so before the song ends. If I find an online example today or over the weekend, I'll send it to you. But you may think of one within the songs of your own music collection, if you do, let me know.