At some point most men will either be offered a prostate examination as part of general health screening, or, it will be advised because of their age (usually 50+) or some problem relating to difficulty in passing urine.
Procedure
The doctor will probably tell you they are going to remove their finger and then offer you some tissue to wipe the lubricant from the anus and buttocks.
What The Doctor is Examining
The doctor moves their finger in a circular motion in order to identify the lobes and groove of the prostate gland. In a normal sized prostate gland they would expect to find the prostate around 2-4 cm long and triangular in shape. They would also expect the prostate to feel firm and rubbery.