I explained it to my class this morning as follows: Endurance classes you try to keep a steady heart rate, around 60 percent (though very few people have monitors). The intervals are longer but less intense, and the rest periods are shorter.
Interval classes have short bursts of really high-intensity followed by longer rest periods.
For today's endurance class I took them up three big (5-6 minute) climbs. After each one there's a recovery then either jumps or sprints to keep things interesting. Each climb was over two songs, so I intentionally made the second song a little faster so the last two minutes or so of the climb would be more challenging. All climbs are a combination of sitting and standing. Here's the playlist:
Rolling Stones: Start Me Up -- warmup
Yael Naim - New Soul: Start climb #1 out easy. About a 3 or 4 on a scale of 1-10. Increase the last minute of the song.