This document provides an overview of Microsoft Windows Identity Foundation (WIF) for developers. It introduces key concepts in claims-based identity including claims, security tokens, issuing authorities, security token services, and relying parties. It explains that WIF is a .NET framework that makes it easier for developers to build claims-aware applications without having to implement identity functionality themselves. The document uses terminology and an example scenario to illustrate how a claims-aware system works with a client retrieving a security token from a security token service before sending claims to a relying party application or service.