Hadath is that which, when produced from or befalls a body, prevents a Muslim from acts of worship for which purification is a requisite, e.g. As-Salah (prayer), circumambulation of the Ka’abah etc. There are two types of Hadath:

Minor Hadath.. It is that which makes  https://www.al-feqh.com/en/wudu-ablution" rel="nofollow - ablution  imperative, like urine, defecation, passing wind and all other nullifiers of https://www.al-feqh.com/en/purification-of-water-in-islam" rel="nofollow - al-wudu ’ (ablution). These will be listed later on in the text. Purification from these is achieved by performing al-wudu’. Allah I says: “O you who believe! When you intend to offer Salah (daily prayer), wash your faces and your hands (forearms) up to the elbows, rub (by passing wet hands over) your heads, and wash your feet up to the ankles. ”(Maidah:6)

Major Hadath .. It is that which makes ghusl (a purificatory bath) imperative, e.g. sexual relations, menstruation etc. Purification from this state is achieved by ghusl. Allah says: “If you are in a state of janabah (i.e. after sexual relations), purify yourselves (by bathing your whole body).” (Maidah:6)

source: https://www.al-feqh.com/en/purification-of-water-in-islam