What is difference between PRG, PRF, and PRP
A Pseudo Random Function is a function that is indistinguishable from a function selected at random from the set of all functions with the same domain and value set. A Pseudo Random Permutation is, similarly, a bijective function that is indistinguishable from a bijective function selected at random from the set of all bijective functions over the same domain. For instance, a cryptographically secure block cipher parametrized by a secret key is a PRP.

The term PRG is otoh most commonly used for stateful functions that are used for generating successive pseudo random strings, e.g. to be used as a key, iv, salt, nonce etc.