We might divide a page template into a header, content, sidebar and footer where these are in separate files. The content will change most between pages, so rather than having a content file, we include the content into a page file which pulls in the individual template files and defines the unique features of that page. The unique features of a page will be the title, description and article content. We can define these at the start of the page template with say PHP code to set the value of variables that are used by the other templates such as the header template. Then we assemble the page by including the required templates and inserting the content.
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.