The word pray is a verb, and it means to talk to God or to any spirit or deity that is the object of worship:
The mother is praying for her son to recover from his illness.
The tribe prayed to the gods for rain.
The noun form is a prayer (referring to the words you say when you talk to God).
The word prey is a noun, meaning an animal that is hunted or caught for food. If a lion attacks and eats a zebra, the zebra is the prey (the lion is called a predator). Mice and rats are prey for animals like snakes and owls.
We also have the phrasal verb, to prey on someone/something - this means to take advantage of them in a nasty, vicious way. For example, criminals who run scams often prey on old people and trick them into sending the criminal their money. People who run sex trafficking businesses prey on young women who are looking for better job opportunities in another country.