Sentinel-2 MSI: MultiSpectral Instrument, Level-1C (COPERNICUS/S2)

Sentinel-2 is a wide-swath, high-resolution, multi-spectral
imaging mission supporting Copernicus Land Monitoring studies,
including the monitoring of vegetation, soil and water cover,
as well as observation of inland waterways and coastal areas.

The Sentinel-2 data contain 13 UINT16 spectral bands representing
TOA reflectance scaled by 10000. See the Sentinel-2 User Handbook
for details. In addition, three QA bands are present where one
(QA60) is a bitmask band with cloud mask information. For more
details, see the full explanation of how cloud masks are computed.

Each Sentinel-2 product (zip archive) may contain multiple
granules. Each granule becomes a separate Earth Engine asset.
EE asset ids for Sentinel-2 assets have the following format:
COPERNICUS/S2/20151128T002653_20151128T102149_T56MNN. Here the
first numeric part represents the sensing date and time, the
second numeric part represents the product generation date and
time, and the final 6-character string is a unique granule identifier
indicating its UTM grid reference (see MGRS).

For more details on Sentinel-2 radiometric resoltuon, see this page.