MapStore is a framework to develop WebGIS applications that can provide advanced viewing tools for maps and geo-spatial data. geOrchestra includes MapStore as the main map viewer for data visualization and sharing.
The official documentation of MapStore is available here. The documentation offers general information about the tools and the pages available in the main MapStore product. Since geOrchestra uses MapStore to build its own MapViewer and MapViewer administration interface, excluding all the other parts of the original product (home page, dashboards, stories...) some of the information in the official documentation may differ from what you will find in geOrchestra.
Anyway you can find useful hints looking at it about some of the tools available in geOrchestra mapstore viewer.
Here the links to the interesting sections for user or for administration UI: