Deutsche Bahn is the company that takes care of the inter-regional train travel across Germany. In Bremen all trains depart from the main train station. Tickets can be purchased at the ticket machines or from the service counters. If you buy a ticket even a few days in advance you can get a savings offer (a “Sparangebot”), which is often much cheaper than a normal ticket. There are also group and weekend tickets, which are cheaper for travel at the weekends or within the region. You can find more information on prices and departure times on the Deutsche Bahn website.