Conversation so far:
what is an area where rainfall is less than 50 cm per year
A desert is a barren area of landscape where rainfall is less than 50 cm/year.
why are deserts bad for life
A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life.

Question: how are the areas formed
Self-contained rewrite: how are deserts formed