SaaS
Software as a Service (SaaS) is a model of software development and deployment in which the software provider licenses a software application to customers as an on demand service. The provider may host the application on their own servers such that access to the application occurs via the web, or they may install the application on their customer's devices with a feature that may disable use after the term of the contract.
http://en.wikipedia.org/wiki/Software_as_a_service