Definitions of religious groups is a contentious subject and so well suited to the form of mutual refinement required by contemporary on-line encyclopaedias such as Wikipedia. Wikipedia defines religion as '... a set of beliefs and practices generally organized around supernatural and moral claims, and often codified as prayer, ritual, and religious law.' This map shows where people who are adherents to any religion live. As with many Worldmapper maps, it is worth comparing it to the population map.
Most of the data for this series comes from the World Christian Database. See the link to 'Religion data source notes' below for more information on the data.