Simply put, Agile Modeling (AM) is a collection of values, principles, and practices for modeling software that can be applied on a software development project in an effective and light-weight manner.  AM recognizes that although all of the following factors are important, when you are following an agile approach to modeling your focus should be on:  

• Individuals and interactions over processes and tools
• Working software over comprehensive documentation
• Customer collaboration over contract negotiation
• Responding to change over following a plan

Agile modeling addresses the following questions (and more):

• What modeling techniques should you apply on a software development project?
• When should each modeling technique be applied?
• How do the modeling techniques fit together?
• What modeling principles should you follow to be effective?
• How much documentation is enough?
• When are hand-drawn diagrams sufficient?
• When do you need a modeling tool?