The goal of agile software, is the creation of software in a "lighter" more efficient manner.  Agile typically involves best practices around the Agile Manifesto... a list of guiding Principles that differentiates agile software development from standard software development.

Some of the principles behind Agile development include :

• Working software is delivered frequently (weeks rather than months)
• Working software is the principal measure of progress
• Even late changes in requirements are welcomed
• Close, daily cooperation between business people and developers
• Self-organizing teams
• Regular adaptation to changing circumstances
• Face-to-face conversation is the best form of communication (Co-location)
• Projects are built around motivated individuals, who should be trusted
• Continuous attention to technical excellence and good design
• Simplicity