OpenStreetMap is community of people creating fully open map database. From roads, shops and rivers to tourism attractions, hiking routes and hospitals, with all kind of detail. Anyone can contribute (and as someone quite involved in OSM: if you want to map something, especially area near you: you are welcome!).
Overture is a new group of companies releasing some datasets on open licenses, but methods used to create them remain proprietary. Some of released data is theirs, many datasets are repackaged OpenStreetMap data.
Ha I was just wondering the same and Overture has a FAQ that answers that exact question;
Overture is a data-centric map project, not a community of individual map editors. Therefore, Overture is intended to be complementary to OSM. We combine OSM with other sources to produce new open map data sets. Overture data will be available for use by the OpenStreetMap community under compatible open data licenses. Overture members are encouraged to contribute to OSM directly.
In some ways OSM is more impressive than Wikipedia.
There’s a gravel path near my house that maybe sees 20 people using it daily. Due to some work done nearby, the path was partially moved a few meters to the side. OSM reflected this new reality the day after.
This really depends on the density of contributors. In Paris every single tree is mapped on OSM, while in more remote areas it’s not rare to see entire roads or even villages missing.
