The sexual response cycle refers to the physical and emotional changes that occur in humans during both masturbation and intercourse. The sexual response cycle is described as a series of stages. The intensity and amount of time spent in each stage is unique to each person. Furthermore, men and women do not experience the stages in the same way. A number of sexual dysfunctions can occur over the course of the cycle. Instead of rigid stages, the cycle has a more fluid motion. Sexual Response Cycle contains four stages: excitement, plateau, orgasm, and resolution.
Phase 1: Excitement
Phase 2: Plateau
Phase 3: Orgasm
The orgasm is the climax of the sexual response cycle. It is the shortest of the phases and generally lasts only a few seconds. General characteristics of the orgasm phase include the following:
Phase 4: Resolution
During resolution, the body slowly returns to its normal level of functioning. Swollen and erect body parts return to their previous size and color. This phase is marked by a general sense of well-being, enhanced intimacy and, often, fatigue. Men need recovery time after orgasm, called a refractory period, during which they cannot reach orgasm again. The duration of the refractory period varies among men and usually lengthens with advancing age. On the other hand, women have no refractory period; which makes it possible for females to have multiple orgasms.
More detailed information can be found at: http://www.webmd.com/sex-relationships/guide/sexual-health-your-guide-to-sexual-response-cycle