Question

what purpose do the poles serve

Answer 1

major amount of water on earth are present in the form of ice which is located at the poles

Answer 2

Earth has two geographic poles: the North Pole and the South Pole.

They are the positions on Earth's exterior that Earth's imaginary rotation axis crosses through these poles. Poles are significant because the North and South Poles are the two coolest climatic zones on Earth, and they influence the climate of the whole planet.  Whereas, the South Pole is positioned on a landmass capped by an enormous icecap.