Simply put, Personal Learning Environments are the tools, communities, and services that serve as individual educational platforms that customers can use to achieve their educational goals.
On campuses that formally support PLEs, instructors or institutions generally provide a framework for student study. This framework might be a desktop application or a web-based service and could include links to web tools, as well as traditional research and resources to which students can add their own network of social contacts and collection of educational resources. Students are encouraged to draw upon these networks and collections of external resources, using them as tools for discovery in an effort to expand their learning experiences beyond campus boundaries.
Obviously PLE is a result of the advancement of Web 2.0 technology and the growing presence of social networking in our lives. To dive further in the subject of Personal Learning Environments, go to the post from Kept-Up Academic Librarian Steven J. Bell.