what do baby's movements mean?!

My baby is a kicky, punchy, wriggly little thing and I love feeling herbin there but sometimes it drives me crazy that I have no idea what she is doing. There are these rapid-fire movements that feel like she's working my uterine lining or cervix like a boxing speed bag and I just sit there trying to imagine what the hell she could be doing that would feel like that?! Does anyone actually know what those feelings are?!