Although 1999 is an exception, in a normal year there is just one full moon for every month. Traditionally, each one had a name. Two of these names are widely known: the full moon nearest to the autumn equinox is Harvest Moon, and the one that follows four weeks later in October is called Hunter's Moon. The others are rarely heard of nowadays, but you can find them if you try, and there are several variations.
November's full moon, for example, is Frost Moon, Beaver Moon, or for some esoteric reason, Mourning Moon. It is followed in December by the Yule Moon or the Winter Moon, and January has the Wolf or Old Moon. February's full moon - when there is one, because this year, as we know, there isn't any - is called the Snow Moon, and is followed in March and April by Storm Moon and Wind Moon (or if you prefer, you can call the latter Grass, or Egg, Moon).
May's full moon is Planting Moon, and that of June is Strawberry, or Rose, or Flower Moon. July has Thunder Moon, and August Grain or Corn Moon, which brings us round to the autumnal equinox and Harvest Moon again.
But these are mundane, banal and unimaginative epithets compared to the names the American Indians used to give their moons. January's full moon for them was Moon When the Cold is Strongest. It was followed by 11 more: the Moon When the Coyotes Live in Fear, Moon When Buffalo Produce their Calves, Moon When Geese Lay Eggs, Moon When the Horse Grows Fat, Corn Tasselling Moon, the Moon When Wild Cherries Ripen, the Moon When Geese Shed Their Feathers, Moon When Corn is Taken In, Big Wind Moon, Moon When Rivers Freeze, and finally, to end the year, the Moon When the Wolves All Run Together, in December.
The Native Americans, of course, had no access to the Gregorian calendar, so the coincidence between their various "Moons" and the months familiar to us now was just approximate. Nor had they any subdivision into weeks, but measured the passage of their time within a Moon in "sleeps", each sleep being punctuated by a sunrise, noon and sunset.
They began their year with the new moon after the vernal equinox, and each was normally just 12 Moons long. Every so often, however, it was necessary for them to add an "extra" Moon to keep their calendar in phase with seasons. This they did after every 30 Moons, and the 13th moon that ended up in that particular year was called the Lost Moon.