http://en.m.wikipedia.org/wiki/Prostate_massage

Prostate massage is also used for sexual stimulation, often in order to reach orgasm. The prostate is sometimes referred to as the "male G-spot". Some men can achieve orgasm solely through stimulation of the prostate gland, such as prostate massage or receptive anal intercourse, and men who report the sensation of prostate stimulation often give descriptions similar to females' accounts of G-spot stimulation.[11][12]Prostate stimulation can produce stronger and more powerful orgasms than solely penile stimulation.[11]
Prostate massage may also be a common sexual practice in couples' sexual lives. The advent of equipment and products for prostate massage encourages people to try it. Many couples though do not purchase such devices but use a finger for anal penetration and prostate stimulation to enhance the man's orgasm. The finger or the prostate massager is introduced into the rectum through the anus and the prostate gland is gently massaged. The main problem in using the finger is that it may be too short to reach the prostate gland. Prostate massage can be performed individually or with the help of a partner. Some men prefer being anally stimulated by their partner during foreplay or after their main form of sexual activity.
