BIM at its foundation is simply an open format for storing construction related information. To extract value from BIM it requires the BIM information to be created, stored on an accessible hub (BIMserver) and made available to stakeholders who are able to utilise it as a foundation to their downstream information needs.
The BIM hub is more than a document management system, it stores IFC (the BIM file format) files as a merged pool (think the contents of many files being merged into one). Because its merged it, it can then be tested and provide tailored (filtered) information views.
The illustration above is not exhaustive and supplementary descriptions for all other stakeholders are listed below.