In February 2001, 17 people met in Snowbird, Utah, for an exchange and discussion about their ways of software development. They followed different methods and agreed on a list on their shared ideas and the basic thoughts they had in common.
This Agile Manifesto states 4 so-called values:
Working Software > Comprehensive Documentation
Customer Collaboration > Contract Negotiation
Responding to Change > Following a Plan
as well as 12 principles:
You can find the unabbreviated version of the Manifesto of Agile Software Development, and some information about the authors. If you agree, you can also sign it.