PHPLIB templates can grant you an amazing ability to abstract the manipulation of data (in the database as well as in PHP) from its final format, whether that format is HTML, XML, WML, or a formatted e-mail, and some of these ways will be explored here.
The most common use of templates is to allow you to change the look and feel of a site quickly without having to delve immediately into alot of PHP variable assignments and print statements.
And it's true that templates allow you to decouple your PHP code and the presentation HTML that's used to display its results but to limit PHPLIB templates to just this mundane chore would be a terrible disservice.
Used properly, PHPLIB templates can grant you an amazing ability to abstract the manipulation of data (in the database as well as in PHP) from its final format, whether that format is HTML, XML, WML, or a formatted e-mail, and some of these ways will be explored here.
There is usually an argument here about whether FastTemplates is really fast, or faster than PHPLIB, and which is better, etc.
I find that PHPLIB templates are more flexible than FastTemplate, don't require that you break nested blocks out into multiple files, and I don't really worry about performance that much, though I've been told that PHPLIB is also supposed to be faster, despite the other's name 'FastTemplate'.
This can almost get religeous, like arguing about using BSD vs Linux, or MySQL vs PostgreSQL, and I really don't want to get into that. Try both, and use the one you prefer: FastTemplates http://www.thewebmasters.net/
Hopefully, in either event, this article will be useful to you =)