A taxonomy is a classification of the standardised terminology for all required and involved terms within a knowledge domain. In a taxonomy, all elements are grouped and categorised in a strict hierarchy and are usually presented by a tree structure.

A thesaurus is a set of controlled vocabulary used within ontologies. In contrast to a taxonomy, the individual elements of a thesaurus are not necessarily required to be semantically related with each other but may well be an independent collection of vocabulary (non-hyponym character).

Topics on the Portal refers to the various subject areas or themes that are covered by the platform. These topics can be related to open source software, e-Government initiatives, policies, standards, and other relevant areas.