Almost all the other software development LIFE cycles either follow a sequential model (eg waterfall model) or an iterative model. But for processes which are a little more complex these models find it difficult to tackle the changes which are large in number and continuous.

Agile model was basically made in order to counter these changes effectively and smoothly. This method is a collection of values, principles and practices that TESTS and provide the feedback to convert it into a new style of development.
Development life cycle:

•  Iteration -1 :Identify, prioritize the potential project, and consider its feasibility.
•  Iteration 0 (Warm Up) : Initiates the project, takes care of the initial input , and emphasis is on building a unit.
•  Construction Iterations: Client participates actively and advises about the expected output, requirements and stuff which is not required by the project.
•  Release: Deploys first release into production, Final system TESTING and trains END users.
•  Production: Operates, supports and identifies defects in the system.
•  Retirement: Removes the system completely from production and migrates the users.

Almost all the other software development life cycles either follow a sequential model (eg waterfall model) or an iterative model. But for processes which are a little more complex these models find it difficult to tackle the changes which are large in number and continuous.

Agile model was basically made in order to counter these changes effectively and smoothly. This method is a collection of values, principles and practices that tests and provide the feedback to convert it into a new style of development.
Development life cycle: