You can make photos, videos, and presentations bigger by connecting Surface Pro to a TV, monitor, or projector. Or, connect to an HDTV and watch movies on a big screen.
The number of external screens your Surface Pro 2 or Surface Pro 3 will support depends on your settings for refresh rate and resolution, and whether the display on your Surface is on or off. For Surface Pro 3, it also depends on which processor you have (i7, i5, or i3).
Reference: “Connect Surface Pro to a TV, monitor, or projector” - http://www.microsoft.com/surface/en-us/support/music-photos-and-video/connect-surface-pro-to-a-tv-display-or-projector