Waterfall Model

Waterfall Model is the most common method used in software testing. It is said to be a water fall method because it is like flowing downwards steadily from step to step.
The main phase or steps in the water fall method are

Conception,
Initiation,
Analysis,
Design,
Construction,
Testing,
Production/Implementation,
Maintenance.
This water fall method actually originated in the manufacturing and construction industries. At that time since no software methodologies existed, this was taken to the software development and testing. the main highlight of this method is one can go to the next step of the development only after completing the on going step.

waterfall testing

Also the developers can go only to one step behind that is the immediately previous phase only. in this method, each phase of the development activity is followed by verification and validation activities. in the waterfall method, the following are the steps involved. you can move on to the next step only when you finishes the present one. the phases or steps are:

Software requirement specification
System and sotware design
Implementation (coding or unit testing)
Integration
Testing and validation
Operation or installation
Maintenance