Smarty is a web template system written in PHP. Smarty is primarily promoted as a tool for separation of concerns. Smarty is intended to simplify compartmentalization, allowing the presentation of a web page to change separately from the back-end. Ideally, this eases the costs and efforts associated with software maintenance.
Smarty generates web content by the placement of special Smarty tags within a document. These tags are processed and substituted with other code. Tags are directives for Smarty that are enclosed by template delimiters. These directives can be variables, denoted by a dollar sign ($), functions, logical or loop statements. Smarty allows PHP programmers to define custom functions that can be accessed using Smarty tags.
Read more about Smarty: Smarty Example, Further Reading