SaaS Software as a Service

SaaS

Software as a Service , is a Web based software deployment model that makes the software available entirely through the web browser
Multitenancy
A multitenant application is server based software that supports deployment of multiple clients in a signle software instance.
SaaS vendors use this principle to serve customers it gives them following advantages

• Support multiple customers from single hardware
• Quicker patches and updates rollout
  

Cloud Computing Services

Cloud computing service generally have following charcateristics

• Accessible via browser (or web services)
• Pay as you go
• No upfront investment

In cloud service can be anything Infrastructure , Software and many more

The above mentioned basic characteristics are common in all kinds of services.