Routers that include a bridging function have been around for a long time. The bridging function was introduced so that routers could forward the unroutable types of traffic. A customer can choose to bridge other routable traffic as well.
Bridges morphed into Layer 2 switches, routers into Layer 3 switches, and bridge/routers (brouters) into Layer 2/3 switches. As before, a customer configures which protocols should be routed and which should be bridged. The difference is that all the actual processing is done a lot faster.
Configuring a Layer 2/3 switch can be a challenge. All the normal router configuration has to be done, along with Layer 2 chores such as VLAN configuration.