MENSTRUAL CYCLES EXPLAIN TO A MAN

I'm going to say something which is really embarrassing here. I know nothing about menstrual cycles. At no point in my life did anybody teach me about menstrual cycles.The only >> insight I have in my life to what a menstrual cycle is is overhearing my sister when I was younger talking about it. Yeah. >> And when I say overhearing, I mean maybe a sentence and then >> maybe my girlfriend once in a while she'll say, "Oh, I'm coming into my cycle or whatever." She'll say, "I'm on my period." That's for most me ...