Today is a #BlueMoon! Which, is the second full moon to occur in any one calendar month.
(Or, more specifically, the third full moon in a season that has four---summer/winter in this case, depending on your hemisphere!)
You see, there's usually just 12 full moons in a year (one per month), and three in a season, but occasionally we get a cool, rare bonus full moon (because a 'lunation', at 29.53 days, is actually a touch shorter than a typical calendar month). So, enjoy the extra full moon today!