A Grid user (e-scientist) group is a research group, scientific center, engineering department, ... which carry out computationally intensive task in their activities and thus can make use of Grid resources provided by external provider.(they can have their own dedicated resources too).
Grid user groups are represented in Grid Plaza by a page created from its domain name, ie. GsdUnavarraEs for group whose domain is gsd.unavarra.es
Also virtual organizations are included in such definition, they will have a name ended in Vo, i.e. AtlasVo.

A Grid provider is an organizational unit which provides computing and other resource facilities to Grid users belong to other organizations.
It can be an independent supercomputing center, the computing facilities deparment of a university,......
Grid providers are represented in Grid Plaza by page created from its domain name, ie. ClusterUnavarraEs for group whose domain is cluster.unavarra.es

Grid resources are access remotely through different mechanisms: Grid services, Remote shells, …
Grid resources identify those essential capabilities needed by Grid users to perform their activities: a software application, computing power, data sets,...
Grid Plaza enumerates resources which are essential for a Grid users to perform their job, if Grid users do not care about certain resource (i.e. Operating System) then it is better for a Grid provider not to list it.