It's also an unlocked phone that you can take to any GSM carrier worldwide.
That smaller black cover you see forms a seal over the battery, the SD card, and the SIM card, to protect them from water damage. You must reseal that cover to make sure the phone's more fragile components stay dry.
The Vortex's 4.5-inch LCD IPS display has a 960x540-pixel resolution. The screen is bright enough to read in direct sunlight with hardly any glare.