SaaS
Today, the terms "Software as a Service" (SaaS) and "On-Demand" describe a technology model where software functionality is delivered over the Internet from a single application instance that is shared across all clients.
On-Demand solutions require only a Web browser for access, eliminating the need to install or maintain software or hardware.
The vendor-client relationship is also fundamentally changed from a one-time transaction (often with hidden costs) to a long-term partnership based on predictable monthly fees - a subscription-based service relationship.