What is the reason for fluid coming out right after intercourse?

Sex: Perhaps you could read your question and see how this is not clear what you are asking or why. Sex leads to orgasm for men which includes ejaculation of semen. Women have lubricating glands that lube up the vaginal tissue and that combined with semen sometimes will leak out after sex. This seems like very simple and basic information so if I am missing the point please re-ask your question.