What is semen (mani), and what is the difference between it and other types of wetness and fluids that exit a woman's vulva, especially those that are light yellow and exit with or without desire, or as a result of effort or walking?

Semen necessitates ghusl and exits with a gush accompanied by desire, followed by lassitude. Its smell is like that of palm spathe or dough. Madhy (pre-ejaculatory fluid) is a thin fluid that exits after arousal of desire; it invalidates ablution but does not necessitate ghusl. Wady (post-urination fluid) is a thick white fluid that usually exits after urination; it is impure and necessitates only what urine necessitates.