Wadi, madhi and mani according to Shari`ah rules

Generally men and women reached maturity or puberity when they were in teens-age. Men usually marked with the experienced to have a wet dreams while women are marked with menstruation. And both the men's or women will experience some physical changes.
Among the changes is the physical development of reproductive organs function of men and women.
When a person is mature, they need to know some terms related to sex, and the rules according to Islam, such as below:

1. Wadi

Is a thick white secretion discharged (by some people) after urination. It tends to be released if one is constipated or has been carrying a heavy load. It is considered impure. 'Aishah said, " Wadi comes out after urination. The person should wash the private parts and perform ablution. It is not necessary to perform ghusl. This is related by Ibn al-Mundhir. Ibn 'Abbas related that "mani (sperm) requires ghusl. As for madhi (semen) and wadi they require a complete purification." This is related by al-Athram. Al-Baihaqi has it with the wording, "Concerning madhi (prostatic fluid) and wadi, he said, 'Wash your sexual organs and perform the same type of ablution as you perform for prayer."'

2. Madhi

This is a white sticky fluid that flows from the sexual organs because of thinking about sexual intercourse or foreplay, and so on. The person is usually not aware of when exactly it is secreted. It comes from both the male and the female sexual organs, although the amount from the latter is usually more than the former. Scholars agree that it is impure. If it gets on the body, it is obligatory to wash it off. If it gets on the clothes, it suffices to sprinkle the area with water, as it is very hard to be completely protected from this impurity, especially for the young, single person.

`Ali (may Allah be pleased with him) said: "I used to excrete madhi, so I asked a man to ask the Messenger of Allah (peace and blessings be upon him) about it. I was shy to do so because of my position with respect to his daughter (`Ali was the Prophet's son-in-law). He (peace and blessings be upon him) said, 'Make ablution and wash your penis.’" (Reported by Al-Bukhari)

3. Mani (Semen/Sperm)

With respect to men, it is a white thick fluid that exist with ejaculation. The sexual fluid of a woman is thin and yellow. Some scholars say that semen is impure, but apparently it is pure, for it is only recommended to wash it off if it is still wet, and to scratch it off if it is dry. `A’ishah (may Allah be pleased with her) said: "I used to scratch the semen off the Messenger of Allah's clothes if it was dry, and wash it off if it was still wet." (Reported by Ad-Daraqutni and Al-Bazzar). It is also related that Ibn `Abbas (may Allah be pleased with him) said: "I asked the Messenger of Allah (peace and blessings be upon him) about semen on clothes. He said, 'It is the same as mucus and spittle. It is sufficient to rub the area with a rag or cloth.'"

Such was the terms that we need to know, especially for teenagers because they are generally embarrassed to ask questions about sex and how the legal according to Islamic law (Shari'ah).

References: Islamonline.net and other Islamic sites.