The DITA map defines the document deliverable's structure. It lists the component topics of that document and defines their position in the table of contents. The map's name is used as the title of the entire document. You cannot have a document without a map.
Map files can be located in many of the views, such as the Todo List and the Search Results view, where they can be locked and released like other types of files.
The DITA Map view and DITA Map Editor, however, provide a hierarchical view of the map tree (the document structure) and its component sub-trees and topics. Once you have locked the map, you can easily drag and drop topics and sub-trees from place to place to re-order the content.