This paper attempts to describe and clarify the meaning of the term Decision Support (DS). Based on a survey of DS related WWW documents, and taking a broad view of DS, a classification of DS and related disciplines is presented. DS is put in the context of Decision Making, and some most important disciplines of DS are overviewed: Operations Research, Decision Analysis, Decision Support Systems, Data Warehousing and OLAP, and Group Decision Support. What is Decision Support?