The initial Zen Cart installation has just one template available for installation. This template is called the classic template, and it's not a good place for newbies, or anyone building a new store, to start.
Why? Well, because the classic template is designed for backward compatibility with previous more table-based versions of Zen Cart. To allow store owners to upgrade it uses two stylesheets and hacks them about a bit to achieve the desired result. Anybody building a new store would do much better to start with a simpler template based on the current template_default included in the release of Zen Cart that you have just installed. Although it doesn't look as good at the outset, it's much easier to understand, edit and maintain, and if you need help from the forum, it is much easier for us to give it.
How do you create a template based on the template_default? There is a step-by-step guide in the wiki.
Warning: at the time of written the links at the top of the page don't work as the articles referenced are not yet back in the rebuilt FAQ.