PASS (Professional Association for SQL Server) Summit is the largest conference for data professional working with Microsoft SQL Server and Business Intelligence stack. Typically, PASS would have the Summit once a year (in the fall) in Seattle, Washington. PASS Summit offers a wealth of knowledge. Each year, there are hundreds of sessions on various SQL Server and Business Intelligence topics presented by industry experts and also Microsoft employees. If you are a data professional, who are working with Microsoft SQL Server and Business Intelligence, PASS Summit is a great event to learn and network with fellow data professionals. If you were unable to attend the past PASS Summits (or if you attended the past PASS Summits and want to relive and review those sessions), you can go to SQL PASS site and watch the past PASS Summit Session Recordings for free. As of the writing of this blog post, you can view recordings for PASS Summit 2015 and older for free (you need to be a member of SQL PASS but the registration is free). Even though they might be a few years old, they are excellent learning resources.
By the way, if you can attend PASS Summit in person, I would recommend it. PASS Summit 2018 is going to be in Seattle, Washington, in November 2018. You can get more information from PASS Summit 2018 site.