The WordPress Importer will import the following content from a WordPress export file:

• Posts, pages and other custom post types
• Comments and comment meta
• Custom fields and post meta
• Categories, tags and terms from custom taxonomies and term meta
• Authors

For further information and instructions please see the documention on Importing Content.

Filters

The importer has a couple of filters to allow you to completely enable/block certain features:

• import_allow_create_users: return false if you only want to allow mapping to existing users
• import_allow_fetch_attachments: return false if you do not wish to allow importing and downloading of attachments
• import_attachment_size_limit: return an integer value for the maximum file size in bytes to save (default is 0, which is unlimited)

There are also a few actions available to hook into:

• import_start: occurs after the export file has been uploaded and author import settings have been chosen
• import_end: called after the last output from the importer