Let us understand what a cloud computing is. It one of the systems which stores the information but the location will not be known by the end user.
So it gives the user a space to store the data but the user cannot identify the source. The user can access from anywhere in the world by connecting to the account.
Saas is one cloud computing model. It is basically a “software distribution model” in which a “third party” can host applications and make it available over internet.