As often happens, I’m showing my ignorance here.
What should I be looking out for?
Smurf’s? 
Oh ha ha, let’s all mock BD’s astrological ignorance. Although Aries are like that.
A Smurf’s what?
A blue moon is the 4th full moon in one season (usually 3) and a supermoon is when it’s closer to Earth so looks bigger.
I know this because I read an article on Newsround about it last week with an online group class. Things we learn doing reading comprehension with students!
Sorry, I just remembered the movie, so thought it was fun.
I thought it was two full moons in one month.
It can be either. This month it can’t be two in the same month because of the date.
According to the article we read, that’s the other definition of a blue moon. But the current one is due to there being more than three in one season.
Article: https://www.bbc.co.uk/newsround/articles/c39k12ygdw3o
Huh. Live and learn:
If you haven’t listened to this whilst tripping on peyote out in the desert under a full moon…well my friend you’ve lived a very sheltered life.