Smarty is a template engine for PHP. More specifically, it facilitates a
manageable way to separate application logic and content from its presentation.
This is best described in a situation where the application programmer and the
template designer play different roles, or in most cases are not the same
person.

For example, let's say you are creating a web page that is displaying a
newspaper article.

- The article headline, tagline, author and body are content elements, they
contain no information about how they will be presented. They are passed
into Smarty by the application,

- then the template designer edits the templates and uses a combination of HTML
tags and template tags to format the presentation of these elements (HTML
tables, background colors, font sizes, style sheets, etc.)

- One day the programmer needs to change the way the article content is
retrieved (a change in application logic.) This change does not affect the
template designer, the content will still arrive in the template exactly the
same.

- Likewise, if the template designer wants to completely redesign the
templates, this requires no changes to the application logic.

- Therefore, the programmer can make changes to the application logic without
the need to restructure templates, and the template designer can make changes
to templates without breaking application logic.