Software as a service (SaaS); It is a software distribution model in which the software applications are hosted over the internet and are made available to the users in return for some fees. Examples are - OneDrive, DropBox, Salesforce, Google Apps, etc.

Simple mail transfer protocol; A protocol used for sending and receiving emails.

Set of programs designed to perform a specific task. It is an executable file (.exe) that can be directly executed on the computer.