When people ask, “Agile Development: What is Agile Development?” they are usually referring to a number of software development and product development practices that fall under the Agile umbrella. The most popular framework for managing projects is Scrum, and the most popular set of agile software development practices are XP practices.
Here are a few XP practices:
Collective Code Ownership
Test Driven Development
What these practices all have in common is that they focus on short feedback cycles, small batches, continuous value delivery, error proofing, continuous learning, and system-wide optimization.