I believe that you all might be aware of the concept of Master Pages in .NET and SharePoint 2007. The obvious benefit of Master pages is that all the pages in a SharePoint site can link to a single Master Page to achieve a consistent look and feel.
Enhancements were made in SharePoint 2010 so that single master page can be used with both Site Pages and Application Pages.
Whenever SharePoint foundation provisions a new site, it creates a special hidden document library known as Master Page Gallery; and creates three new Master Page instances:
v4.Master: This is the primary master page used in SharePoint 2010 sites. Ex: Team Site Master page. It includes element such as Site Actions menu, the breadcrumb trail, the Ribbon, the welcome menu, the site icon, the topNav bar and the quick launch.
minimal.master: minimal.master is a page layout without any of the chrome that is included in v4.master.
default.master: default.master is a master page designed to support a feature known as visual upgrade, which assists in upgrading SharePoint 2007 sites to run within SharePoint 2010 farms.