There are hundreds of different kinds of LCDs, the ones we'll be covering here are character LCDs. Character LCDs are ideal for displaying text. They can also be configured to display small icons but the icons must be only 5x7 pixels or so (very small!)
Here is an example of a character LCD, 16 characters by 2 lines:
The graphical LCD has one big grid of pixels (in this case 128x64 of them) - It can display text but its best at displaying images. Graphical LCDs tend to be larger, more expensive, difficult to use and need many more pins because of the complexity added.
This tutorial isn't about graphical LCDs. Its only about text/character LCDs!