SharePoint 2010 Web Pages
Your SharePoint 2010 team site is really just a collection of web pages. You have two different types of web pages for displaying your content — Wiki Content pages and Web Part pages.
If you're familiar already with SharePoint team sites, you’ve probably worked with Web Part pages. In SharePoint 2010, Wiki Content pages are now the default web page type. They are stored in a wiki page library dubbed Site Pages.
Wiki pages in SharePoint 2010
You may be wondering, why wiki pages? A wiki is a site that’s intended to be modified by many people. Think about the very popular wiki site Wikipedia. Everyone can contribute to Wikipedia. That also sounds like a SharePoint team site. Team sites use wiki pages to make it easy for everyone on your team to share information.
Only members of your team site’s default Members group have permissions to modify wiki pages. If you want some people to be able to read your wiki pages but not edit them, add those users to your site’s default Visitors group.
A Wiki Content page consists of a very large text page where you place your content. In this large text box, you can place almost any kind of content imaginable — freeform text, tables, hyperlinks, images, even Web Parts. A Wiki Content Page combines the best aspects of a typical wiki page with a Web Part page.
You can create other Wiki Content pages for your site by choosing Site Actions→New Page. These new Wiki Content pages are also stored in the Site Pages library.
You can create additional wiki page libraries if you wish to manage a specific wiki topic in your site.
Web Part pages in SharePoint 2010
The traditional type of SharePoint page contains various zones in which to place Web Parts; it doesn't have the same editing experience as the Wiki Content page. The Web Part page, however, has been enhanced to allow for easier text editing and image insertion.
Web Part pages are also saved to libraries. You may want to create a document library to hold your Web Part pages before you create them, unless you want to save them to the Site Pages library.
Many of the system pages that you see in SharePoint team sites are actually Web Part pages. Pages for displaying, editing, and viewing list properties are Web Part pages. These pages are list forms.
Any web page that has the path _layouts in the web address is one of SharePoint’s application pages and can’t be customized.