Besides content, all linked or child records (for selected content) will be deleted to prevent creating orphaned rows in the database.
For instance, for posts, that's posts, post meta, and comments related to posts. The delete process does not call any WP hooks such as before_delete_post. Choosing a post type or taxonomy does not delete that parent object - it deletes the child objects. Parent objects are defined in code. If you want to remove them, remove their code definition.
When media is deleted, files are left in the uploads folder. To delete files, use the Clean Uploads Folder tool.
Deleting users does not affect the current, logged-in user account. All orphaned objects will be reassigned to him.
At the moment there are no additional filters available like "delete all posts older than X days".