The Swiftype WordPress plugin will index all registered post types that are not excluded from search.
Typically, this means they have been registered with the
public flag set to
true (as this is a shortcut for
exclude_from_search being set to
false) but it is possible to register a private post type that is included in search. See
get_post_types for details.
The default WordPress post types that are public are
Additionally, an individual post must have a
publish to be indexed. Attachments have a
inherit and so are not indexed even though they are public.