Agile software development proceeds in mini-projects, known as iterations, lasting about two to four weeks. Every iteration delivers working, implementable, software that adds value to the business.

Each subsequent iteration is an opportunity to make a course correction based on fresh information and current priorities in the business. Iterations are implementable, production ready, software and deliver immediate business benefits.  There is no need to wait for the end of the project to realize return on investment

Traditional methods – long delay before benefits are realized
 

Agile methods – earlier, and increased, benefits from early, partial, implementations