What is an Orgasm and How can one know they've had one?

I'm not a sex expert as had my first sexual relationship when I was close to 26. Got pregnant, had my baby (my son is now 3 going on to 4 in a few months) and stopped having sex until a week ago. My sons father (only partner but we were not together until a week ago) asks if I cum and I say yes but honestly I don't know if it did. I know I am always dripping when we are done but I always think thats me being "wet". Help please.