RT is an enterprise-grade issue tracking system designed to let you intelligently and efficiently manage tasks, issues, requests, defects or anything else that looks like an "action item."
RT is used by Fortune 100 companies, one-person businesses, government agencies, educational institutions, hospitals, nonprofits, NGOs, libraries, open source projects and all sorts of other organizations on all seven continents. (Yes, even Antarctica.)
You're seeing this screen because you started up an RT server without a working database. Most likely, this is the first time you're running RT. If you click "Let's go!" below, RT will guide you through setting up your RT server and database.
If you already have a working RT server and database, you should take this opportunity to make sure that your database server is running and that the RT server can connect to it. Once you've done that, stop and start the RT server.