The Corpus or Corpus of Terminology is the documentation that describes the knowledge around a set of terms and concepts. It is typically governed by conventions that are specified by a group of terms communities, such as TOIP's Concepts and Terminology Working Group.
The purpose of having a corpus is that it allows for the development of tools that support authors and groups of people to better communicate, by enabling them to refer to the definition of a term whenever that term is used. This is particularly beneficial when a specific term can be interpreted in different ways (according to different definitions).
Tools that we envisage will query for terms from the corpus, and use that e.g. to create a custom glossary document, a terminology appendix in a paper you write, or as a resource from which you generate pop-up balloons in a website you create.
Part of the description is taken from TOIP CTWG