Agile and Waterfall differences

One of the most important differences between the agile and waterfall approaches is that waterfall features



distinct phases with checkpoints and deliverables at each phase, while agile methods have iterations rather


than phases. The output of each iteration is working code that can be used to evaluate and respond to


changing and evolving user requirements.
Waterfall assumes that it is possible to have perfect understanding of the requirements from the start. But



in software development, stakeholders often don’t know what they want and can’t articulate their requirements.


With waterfall, development rarely delivers what the customer wants even if it is what the customer asked for.


Agile methodologies embrace iterations. Small teams work together with stakeholders to define quick prototypes,


proof of concepts, or other visual means to describe the problem to be solved. The team defines the


requirements for the iteration, develops the code, and defines and runs integrated test scripts, and the users


verify the results. Verification occurs much earlier in the development process than it would

with waterfall, allowing stakeholders to fine-tune requirements while they’re still relatively easy to change. 

 
refer: http://www.serena.com/docs/repository/solutions/intro-to-agile-devel.pdf