Copyright © 2001 by Thomas Hurst
The purpose of a templating system is to ease the seperation of presentation from content, which can improve readability, maintainability, extend human lifespan by 400% and bring about world peace.
There are lots of methods of doing this - XML/XSL, Smarty, FastTemplates, etc. SimpleTemplate is yet another one.
Nested blocks - rather than leave it up to you to make your PHP work out how everything fits together, the template system does most of the work for you.
Variable modifiers - SimpleTemplate can apply several filters to variables before entering them into the output, adding a further layer by which to help abstract output format from your PHP code.
Fast - it doesn't just use a simple str_replace() loop, but splits the template down to a more suitable internal format.