The JW Embedder currently offers 3 modes:
Flash mode - The original JW Player mode. Uses the Flash Platform to playback streaming and progressive video, images, and sound.
HTML5 mode - HTML5 offers support on the most up-to-date browsers and devices such as the iPhone, iPad, and Android.
Download mode - Download offers the widest range of compatibility, allowing users with almost any video capable device to view the content.
The player can only run in one mode at a time, and certain features (including plugins, skins, and the JavaScript API) are disabled in download mode.
From
http://www.longtailvideo.com/support/jw-player/jw-player-for-flash-v5/18508/jw-embedder-modes
