SNAP is the common software platform for the three Sentinel Toolboxes which are developed by the European Space Agency (ESA) for the scientific exploitation of the Sentinel-1, Sentinel-2 and Sentinel-3 missions.
The project page of SNAP and the sentinel toolboxes can be found at http://step.esa.int. There you will find a tutorial about the usage of the application, a forum where you can ask questions and lots of other interesting things.
The intention of the development is to primarily support the Sentinel missions for not only research but also in an operational context. In addition, a great deal of the development will be to improve and produce a common application platform for all toolboxes for the next 10 years.
The Toolboxes are be based on the proven BEAM/NEST architecture inheriting all BEAM and NEST functionality including multi-mission support for SAR and optical missions and provide an evolutionary update to the architecture to support ESA and third party missions for years to come. In practical terms this means that all three toolboxes are based on the extension of the existing open source BEAM and NEST toolbox framework. The common platform is jointly developed by SkyWatch, CS-FR, CS-RO and Brockmann Consult.
How SNAP and the toolboxes can be built from source is documented in our Developer Guide.