Both. A quick way to see if the Videos app supports any particular video site is to paste it into a post and see if IPB4 turns it into an embed code automatically. If it does, then the Videos app supports that particular site. Here is a rough copy from the source code itself on the current oEmbed sites IPB4 supports.
'youtube.com' => 'https://www.youtube.com/oembed',
'm.youtube.com' => 'https://www.youtube.com/oembed',
'youtu.be' => 'https://www.youtube.com/oembed',
'flickr.com' => 'https://www.flickr.com/services/oembed/',
'flic.kr' => 'https://www.flickr.com/services/oembed/',
'hulu.com' => 'http://www.hulu.com/api/oembed.json',
'vimeo.com' => 'https://vimeo.com/api/oembed.json',
'collegehumor.com' => 'http://www.collegehumor.com/oembed.json',
'twitter.com' => 'https://api.twitter.com/1/statuses/oembed.json',
'instagr.am' => 'https://api.instagram.com/oembed',
'instagram.com' => 'https://api.instagram.com/oembed',
'soundcloud.com' => 'https://soundcloud.com/oembed',
'open.spotify.com' => 'https://embed.spotify.com/oembed/',
'play.spotify.com' => 'https://embed.spotify.com/oembed/',
'ted.com' => 'https://www.ted.com/services/v1/oembed',
'vine.co' => 'https://vine.co/oembed.json',
'facebook.com' => array(
'(\/.+?\/videos\/|video.php)' => 'https://www.facebook.com/plugins/video/oembed.json',
0 => 'https://www.facebook.com/plugins/post/oembed.json',
),
'gfycat.com' => 'https://api.gfycat.com/v1/oembed',
'dailymotion.com' => 'http://www.dailymotion.com/services/oembed',