This list defines what per object meta data the Catalog will store. When objects get cataloged, the values of any attributes they may have which match a name in this list will get stored in a table in the Catalog. The Catalog then uses this information to create result objects that are returned whenever the catalog is searched. It is important to understand that when the Catalog is searched, it returns a list of result objects, not the cataloged objects themselves, so if you want to use the value of an object's attribute in the result of a search, that attribute must be in this list

It is generally a good idea to keep this list lightweight. It is useful, for example, to keep the 'summary' meta data of a text document (like the first 200 characters) but not the text content in it's entirety (it is useful in this example to index the text contents, which is configured in the Indexes View tab). This way, the summary data may be shown in the search results.