When a platform is hosted on a cloud server and is designed for the open market where customers can get access to the platform with their unique credentials, such a platform or software is called software as a service or more commonly refered as SaaS platform.
To get access to SaaS platform, users usually buy the subscription to the platform which can be for a day, week, month, quarter or annual. This subscription can also be based on different functional access of the platform where certain functions would be free to access and others would be paid. To replace software offerings that had to be owned by an entity to get access to it, SaaS was introduced as a cost-effective software licensing alternative.