Developing a business application breaks out into five stages

1. Gathering Requirements
2. Architecture
3. Development
4. User Testing
5. Deployment

This model is helpful in understanding the process but there is a lot of leakage between the steps. In reality, new features get added during user testing. Requirements for those features must be gathered as the rest of the app hurtles toward deployment, etc. Despite this, the model is a helpful guide to the process.

First: Gathering Requirements: aka The Big Idea