it's not rlly a genre, it's a demographic. Shounen series are targeted towards 12-18yr males. While generalizations can be made about what shounen series are about and stuff, they are not rules and there are many exceptions.
Sorta like how seinen is known to be pretty dark and mature, but then k-on is a seinen as well.
It kinda is and isn't (well I get why it mostly mistaken as action since most shounen are action) but shounen means "Young Boy" or "Boy" any category can fit into shounen if the mc is a boy, so basically a romance anime can still be considered a shounen if the main lead is a boy... vice versa with shoujo, shoujo doesn't mean romance it just mean "Young girl" or "Girl" so an action anime can be considered shoujo if the main lead is a girl.
wht does shounen mean like wht kinda genre is it