LinkedIn is a professional networking platform that allows users to connect with colleagues and find job opportunities. It has over 75 million members worldwide, with half of users being in decision-making roles. To get the most out of LinkedIn, users should create a complete profile, build a network of connections, join relevant industry groups, and use the site to research companies and search for jobs. Staying active on LinkedIn even after finding employment can help users learn about new opportunities through their expanded professional network.