Harvest Moon is the full moon closest to (or, by some sources, the full moon following) the Autumnal Equinox on 22 September. This was a classic traditional time for bringing in the harvest, especially since the added moonlight meant the work could run later.
Because of precession and those sorts of things, the fall full moons rise much closer together from night to night — in the US, about 25-30 minutes later each night (10-20 or so in Canada), versus an average of 50 minutes later during the course of the year. On a clear night, there can be moonlight nearly from sunset to sunrise.
If the Harvest Moon comes in October (which it does about a third of the time), then the full moon of September is called the Corn Moon.
The full moon that follows the Harvest Moon is the Hunter’s Moon. The night light, the freed-up labor from the harvest a month before, the fallen foliage and barren fields, and the need to provender for the winter, made this a traditional time to hunt. This year’s Hunter’s Moon was last night.
The names may (or may not) come from the names used by the Algonquin Indian tribes.
cool.