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.
With website templates you can get the best of both worlds. You can get something that is low-priced, was made by a professional developer, and is going to have at least a semi-professional look that should suit you just fine. These designs have been developed exclusively for professionals and individuals who want a simple solution. You will be able to add your own images, content, etc. to the site. As far as price goes though, it can definitely fluctuate. You can find low-priced templates or higher priced website templates.