Lubricant
When a man and a woman get sexually aroused a clear fluid is released from the man’s urethral opening and from the woman’s vagina. This fluid, particularly that from the vagina, is important as it helps the penis to slide in and out during intercourse, otherwise it can be painful if it gets too dry. The amount of fluid that is released varies, so sometimes it may be necessary to use a lubricant. Tubes of lubricant can be bought at a chemist’s.