A composition is stored as a file or a group of files, depending on its state. For a newly created composition, a file named <compname>.txcomposition will exist on the file system. Within Composite, you will see only the name part of the file, not the extension. Whenever a new version is created, a new directory named <compname>.txversions is created and contains additional files, one for each version. Also, if you happen to have some Raster Paint nodes in your composition, another directory, named <compname>.txpaintstrokes is created to store the paint strokes. By default, the browsers in Composite do not show the versions and paint strokes directories. To see them, you must deselect the Collapse Compositions option.