SaaS is used to describe a model of software deployment that uses the web to deliver applications on an "as-needed" basis (Pearlson, K. & Saunders, C., 2013, pg. 385). It usually runs on a computer on the Internet, rather than on the customer's computer, as is accessed through a web browser. PaaS is the set of tools and services designed to make coding and deploying those applications quick and efficient. IaaS is the hardware and software that powers it all - servers, storage, networks, and operating systems.