* Touch Panel Digitizer: If the top touch panel or glass top is cracked or broken but the image under it is fine,then you only need the Touch Panel.
* LCD Display Only: If the image under the glass is broken and the touch pancel is NOT then you only need an LCD display.
* Complete Screen with Touch Panel and LCD: If the top touch panel is broken and the LCD image is either black liquid or cracked you need a complete screen
The Digitizer can be bought for about $16-$20, the LCD is a little more expensive, around $35-$40. I would see which description above fits your device and then go from there