Cumming is when a guy ejaculates and orgasm is when women have muscle spasms caused by the clitoral nerve transmitters. But they are interchangable in common talk.
As far as if you know or not you had an orgasm, if you have to ask, then you didn't. Some women go their entire life w/o ever having an orgasm.
The spurting of body fluids from a women does not guarentee they've had an orgasm.
An orgasm can be reached by many ways (clitoral stimulation, labia stimulation,etc. Even breast stimulation) but it always the result of the clitoral nerve endings. The clitoris, though just useally a small round protrusion, is actually about 2.5" long and is "y" shaped with the bottom of the "y" being exposed. The two branches of the "y" are giant nerve transmitters that attached to a nerve center for the abdomen, buttocks, and leg muscles. That is why most womens, abs, butt, and thighs will contract and tighten during orgasm.