SharePoint uses the master page concept to achieve a uniform look and feel across a site, and you will find yourself extensively working with master pages in SharePoint.
Did You Know?
Master pages were introduced in ASP.NET 2.0 and allow you to create a consistent layout for the pages in your site.
A master page defines user interface elements common across the site. In addition it defines content placeholders that can be overridden by the individual pages to achieve the user interface specific to the pages. This allows you to have a consistent look and feel across the site. You can use a single master page for the entire site or use multiple master pages. You can also have nested master pages. All this gives you ...