"Sentinel-2" does not refer to a single satellite, but to a pair of satellites. The first satellite 2A was launched on 22.06.15, 2B was launched on 07.03.17. They circle around the earth in a polar sun-synchronous orbit at an altitude of about 786 km. The overflight times are similar to Landsat and SPOT-5. This makes the data sets more comparable and also allows time series analyses.
Artistic representation of Sentinel-2. Right: Image from the Taunus (Hesse), each in a different combination (red-green-blue, RGB) of different spectral bands.
Some key facts about Sentinel-2:
For getting to know more about it, the Sentinel Playground (Sinergise Ltd.) is recommended.
Global coverage of Sentinel-2 in a video animation (ESA):
Rostock from above... Sentinel-2 Color Infrared (CIR) False color composite, RGB: 8-4-3. The arrow marks (approximately) the campus area of the University of Rostock.
Global coverage with Sentinel-2 as 100x100 km tiles.