Template page for website

I am building a website for online calculators - [login to view URL] I would like have a SINGLE template, which has the outside formatting of the about us page ([login to view URL] - without the quick inquiry section) that is linked to all the other pages. This will enable me to change the look of all the pages on the website by only changing the template. In other words, the outer edge of every page will be the same file, and the centre part of the page will be unique to each page. As such, I would need to files 1. The template, which has the same formatting as the rest of the site, and a space in the middle for the unique page's contents. 2. The middle part of a page, which has space for its unique contents - but the outside links back to the template page for its formatting.