What's the difference between an iPhone's glass and LCD?

A: Digitizer (aka Touch Panel) - the glass part of the screen covering the LCD display
   
    LCD (Liquid Crystal Display) - the part of the screen displaying the image

    You may have a cracked digitizer, and the image will display perfectly.

    If you have a cracked LCD, the display will be distorted and both the LCD and digitizer will need to be replaced.