There are two types of orgasms: clitoral orgasm and vaginal (also called G-spot orgasm). The first is achieved through stimulation of the clitoris and the latter is attained through stimulation of the G-spot.

The G-spot is located about an inch inside the vagina. Both the clitoris and the G-spot can be stimulated during intercourse and foreplay. The clitoris gets stimulated by the vaginal wall which goes back and forth during intercourse.
The arousability of the clitoris and the G-spot depend to a large extent how good blood circulation is in the pelvic area and how strong your pelvic floor muscle is.

Basically the better shape your pelvic floor muscle is in the easier it will be to get stimulation, because muscles that are in shape need more blood going through them - which increases sensitivity and arousability for both the G-spot and the clitoris. Secondly and espescially for the clitoris, a strong pelvic floor muscle increases direct stimulation.