What is the difference between semen and normal discharge in women, and which of them necessitates Ghusl?

Semen: Its characteristics are: a thin, yellowish (or white for some women) liquid, its smell is like dough, and it exits with pleasure, followed by a cooling down of desire. It is pure, but a ritual bath (ghusl) is obligatory after its emission.

Pre-seminal fluid (Madhi): A transparent, sticky fluid that exits upon arousal without pleasure or cooling down. It is impure, nullifies ablution (wudu'), and whatever part of the body it touches must be washed. It is sufficient to sprinkle water on clothing to purify it.

Vaginal discharge (Rutubah): Transparent secretions that exit from the uterus. They are pure and nullify ablution. However, if they are continuous, the woman performs ablution for each prayer after its time has begun.