This document discusses LinkedIn, the world's largest professional social network. It has over 277 million members and allows users to build professional connections, find jobs, promote businesses, and access learning resources. The document provides tips for using LinkedIn such as getting a custom URL, writing an effective headline and summary, choosing a good profile photo, showing achievements, adding multimedia, using relevant keywords, posting consistently, and engaging with groups. Background photos should be under 8MB and 1400x425 pixels for the best display.