Ghusl is the complete washing of the body required to return to a state of purity — for example after intimacy (janabah), and for a woman after menstruation. The Qur'an commands purifying yourself in this state before prayer.
“...And if you are in a state of janabah, then purify yourselves...”— 5:6 (Saheeh International)
Ask Noor can walk you through the steps of ghusl, the intention, and what makes it obligatory.
Ask Noor — free on the App Store