[TYPO3] Conceptual questuon DS and TO

[Nader Emami Salut]

Hello

I would ask a question (conceptual one) about DS/TO. I am learning TYPO3 
and now I am busy withFuturistic Template Buliding (FTB). I kan not good 
understand from this document what the relationship between DS/TO and 
HTML template is. Till now I have understand that TS makes e web page 
from DB and HTML template. Now I don't know why we should use 
TemplaVoila! Is this actually neccessary to learn if somebody would liek 
to make some web site? Because I have been become cofuse of unclear 
explanation about this subject.
Would somebody explain me about this concept?

Regards
Nader