Watter on the yird turns intae gas an fleets up intae the lift (evapoorates). Thare, whan its is caulder, the watter coondenses: it chynges frae a gas tae dribs o watter or creestals o ice. We see thae dribs o watter as cloods. The dribs faws back doun tae the yird as rain, an syne the watter evaporates again. This is cried the "watter cycle".
Whiles cloods on ither planets is juist a hatter o gases.