LinkedIn is a professional networking platform with over 60 million active users that can be used to connect with others, find jobs and recruiters, join groups, and share referrals. The document provides tips for using LinkedIn to showcase expertise through an optimized profile, including having a headline with an elevator pitch, a summary using the PAR format, recommendations, imported content from other sites, and engagement in groups and events to build credibility and contacts. Additional resources for using LinkedIn in a job search are provided.