Do i need to know HTML to run a website?

No you do not have to know anything about web site coding in order to run your own web site. A CMS web site has all the tools built in you will need to manage your web site. Just by typing into a form and pressing save will add content to your web site. Effectively you are running your own site. Another great benefit of CMS sites is that you can extend the web site services with modules. These can be downloaded or created to provide particular services that may not be included in the default web site framework.

Basically your web site grows as you do.