EXPLANATION/ANSWER:
A Desert is an area with very limited rain or little to no water source. It is also very hot during the day and very cold during the night. Plants like cactus survive in it because they have evolved to adapt to a desert. There are also very few animals that can survive in the desert like small lizards and insects.
Plants are few and far between in a desert because there are very limited spaces where there is at least moisture in the air or a little bit of water.