A repository contains collections to be shared. A collection is a set of resources that belong together. Either because they can be used to create a coherent map design or do a specific task, or because they form a natural group.

The items that supported by the QGIS Resource Sharing plugin are (plugin version in parenthesis):

Item Folder Notes
Raster images image Image files that can be used as Raster image markers and Raster image fills. Can be referenced from symbols and styles.
SVGs svg SVG files that can be used as SVG markers and SVG fills. Can be referenced from symbols and styles.
Symbols symbol XML files that can contain marker, line and fill symbols and also colorramps, textformattings (0.14) and labelsettings (0.14).
Layer styles style QML files.
Expressions (0.15) expressions JSON files with user expressions (QGIS 3.12 and later).
Processing scripts processing Python processing scripts.
Models (0.10) models Models for the Graphical modeler.
R scripts (0.9) rscripts Processing R Provider plugin R scripts.
Checklists (0.16) checklists Checklist files for the QGIS Dataset QA Workbench plugin.

Note that you can include other QGIS resources in the repository (composer templates, project files, …) as well. They will be available in the collection directory, but the plugin will not do anything with them.