Ripped straight from the steam store page:
Moonlighter is an Action RPG with rogue-lite elements that demonstrates two sides of the coin – revealing everyday routines of Will, an adventurous shopkeeper that secretly dreams of becoming a hero.

As the description suggests, by day you are a shopkeeper selling your wares. And by night you raid the dungeons to get more items to sell at your quaint little shop! This game is kind of like a mix between Stardew Valley and The Binding of Isaac, so if you liked either of those games, you might want to consider giving this a go.

I've barely scratched the surface of the game myself and I find it very enjoyable, juggling prices of my wares to see what is a good price to sell them at, choosing different equipment to upgrade over others, and just running around smacking monsters with my broomstick!