Difference between using lcd in 4-bit and 8-bit mode
LCD stands for liquid crystal display. Lcds come in many sizes 8x1 , 8x2 , 10x2 , 16x1 , 16x2 , 16x4 , 20x2 , 20x4 ,24x2 , 30x2 , 32x2 , 40x2 etc . Many multinational companies like Phlips, Hitachi, Panosonic make their own special kind of lcd's to be used in their products. All the lcds can be used in 8-bit as well as 4-bit mode.
The major difference is between initializing commands and data Pins. Initializing commands are commands that initialize the lcd(In 4-bit or 8-bit mode, Cursor on or off etc). Refer to datasheet of lcd if you want to learn about lcd initializing commnds OR just go through this simple tutorial.
LCD IN 4-BIT MODE
Commands used to initialize the 4-bit lcd mode
LCD IN 8-BIT MODE
Commands used to initialize the 8-bit lcd mode are