OpenStreetMap is a new layer in Bing Map, and the latest map app dubbed "OpenStreetMap" loads OSM maps as a new map style option. OpenStreetMap follows a similar concept as Wikipedia, but for maps and other geographic facts. This information gets uploaded to OpenStreetMap's central database from where it can be further modified, corrected and enriched by anyone who notices missing facts or errors about the area. Users can still perform searches atop of OSM map layer. Once OSM Maps are rendered, users will find OSM map option listed in the map types so if you switch to Bird's Eye or some other native Bing map types, you can easily return to OSM map style. Of note, we are using the Mapnik map style from OSM (one of the many map styles available to open source users) to create our OSM map type.
More Info: OpenStreetMap