Does anyone know how to use SMARTY?

I am trying to understand this whole smarty thing but I'm not getting. I am trying to redesign my entire site ( http://www.HostUltimo.com ) but simply do not understand the purpose of this smarty template thing. The reason for me doing this on my own and not hiring someone to do it for me is because I am using exponentcms ( http://www.exponentcms.org/ ) and no one seems to know how to design it plus i do not have much money in the first place.

All i'm asking for is for someone to explain the smarty template design thing on lament terns. Do not have to be in cave man terms because i am familiar with some html/php coding and so forth.