The two main parts of a template are the content management code and the theme. These should be kept separate so that the theme can easily be changed without affecting the structure. For example, the styles should be defined in an external style sheet and not embedded in the HTML code of the pages. The structure of a website will be defined by a set of templates. It is good practise to make the templates modular rather than having page templates containing all the code for each page. This allows site-wide changes to be easily applied. For example, the footer may be mostly identical between pages.
You can also find website templates that are designed for content management. This means if your goal is to create a content-based website, such as a blog, you will have an easy time managing the content. You will be able to easily create and publish unlimited blog posts, and all without having to have knowledge of web programming like HTML, CSS, PHP, etc. One of the best templates for content management would be WordPress and also Joomla. There are other options available as well that you might be more comfortable with.