All core features are directly associated with a functional area of the edit screen, such as the editor or a meta box. Features include: 'title', 'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt', 'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
Additionally, the 'revisions' feature dictates whether the post type will store revisions, and the 'comments' feature dictates whether the comments count will show on the edit screen.
A third, optional parameter can also be passed along with a feature to provide additional information about supporting that feature.
Example usage:
add_post_type_support( 'my_post_type', 'comments' );
add_post_type_support( 'my_post_type', array(
'author', 'excerpt',
) );
add_post_type_support( 'my_post_type', 'my_feature', array(
'field' => 'value',
) );