Catalogs are subpage types. Subpages are pages of reference information that are attached to encyclopedia articles. The catalog subpage is an optional subpage that can be found on the articles listed below.
These catalogs list facts in a table such that it is easy to scan and find information. The type of information that is included in these catalogs is entirely dependent on the subject that is being cataloged. Generally information that can easily be tabulated and is descriptive of the subject of the main article is included in these catalogs. For example in a catalog of planets and moons, we would list information such as diameter, distance from sun (or earth), elements in atmosphere (if any), etc.
We have only recently started adding subpages to our content, so we don't have that many yet, and most are not at all complete. But we've made a start!