Smarty is what is known as a "template engine". In other words, if you put all your data-gathering in one place you can then send the information for a page to the templates you make with Smarty, and get a page generated neatly every time. Some template engines slow you down, but Smarty's templates actually compile into PHP, so there is little difference if you use them or not. Just more flexibility to your interface without changing your backend code.

__________________
Programmers are in a race with the Universe to create bigger and better idiot-proof programs, while the Universe is trying to create bigger and better idiots. So far the Universe is winning. - Rich Cook