Flutters vs. Movement/kicking??

Marie 🍼 Pregnant with #2
I'm a FTM and I'm 16w2d. I've heard that you don't really feel movement so early when it's your first baby, but my question is what is the difference because a flutter and a full on movement or kick? Or is it all the same thing, just that the baby is different sizes? I'm curious because I'm feeling something that I know isn't just gas.