This document discusses professional learning networks (PLNs), which are groups of people that individuals engage with online to share knowledge and information. A PLN is a personal collection of contacts that can provide guidance, learning opportunities, answers to questions, and their own expertise. Benefits of PLNs include learning new things, collaborating with others, and getting validation. The document provides examples of different types of online tools and services that can be used to develop a PLN, including Twitter, Diigo, SlideShare, and Flickr. It emphasizes contributing to the PLN by sharing resources with others.