Question

how does a water kept in an earthen pot becomes cool during summers

Answer 1

due to small pores in pot the water came out from them and then evaporates which leaves a cooling effect therefore the water kept in it get cool.

Answer 2

An earthen pot (matka) has many small pores. Water seeps out through them and evaporates from the surface of the pot. The energy needed for evaporation is taken from the water kept in the earthen pot. As a result, water kept in earthen pot becomes cool.