Along with the U-Bahn, the S-Bahn forms the backbone of public transport in Berlin. It serves the city area of Berlin and connects it with the surrounding region. The rapid city transport system provides high transport capacities and is able to move large flows of traffic over large distances at relatively high speeds.

Within the Verkehrsverbund Berlin-Brandenburg (VBB), a system of collaboration between the various public transport providers, the Berlin S-Bahn has a fixed place between the regional transport system provided by the Deutsche Bahn, which serves mainly the surrounding region, and the transport services of the Berliner Verkehrsbetriebe (BVG), which deal with the fine distribution of the traffic flows within the city.

S-Bahn Berlin GmbH regards itself primarily as a service provider and aims to fulfil the requirements and wishes of its customers. Its customers are, on the one hand, the governments of Berlin and Brandenburg, as they commission the transport services of the S-Bahn. Its customers are also, of course, the passengers. Around one million people use the S-Bahn on any workday.