Steps to create a Layout Page

First Lets see what are Page Layouts:

1#.Page layouts are templates that define content structure for a page and are always associated with a content type.
2#.A content type contains a document template, data columns, workflows, and other information that completely define a document.
3#.The publishing feature of MOSS uses a single root content type for publishing called Page.
4#.All of the page layouts inherit from this base. Here’s how to create a new page layout in MOSS.

Now lets see the steps to create the Page Layouts:

STEP 1: Define Site Columns
The individual content elements that appear in a page layout are derived from site columns. When you create a page layout, you can use any of the site columns already defined or define your own.

STEP 2: Define a Content Type
Page layouts have a direct relationship to a content type defined within the site. The content type is a collection of site columns, a page template, workflows, and other information that determine the appearance and behavior of a page layout. In order to create a page layout, you must create a new content type that derives from the existing Page content type. Inheriting the Page content type allows the new page layout to function correctly within the MOSS content management Feature.

STEP 3: Create the Page Layout
Page layouts are stored in Master Page and Page Layout Gallery. From this gallery, you can create a new page layout and associate it with a content type.This process makes the site columns that are defined for the content type available to the page layout as field controls that you can place on the page with the SharePoint Designer.

STEP 4: Edit the Page Layout in SharePoint Designer
Once you have created the new page layout, you must open it in the SharePoint Designer so that you can add the desired field controls. The site columns you defined as part of the content type become available in the SharePoint Designer as field controls that you can place on the page layout.

STEP 5: Publish the New Page Layout
Once the page layout is created, you must publish and approve it so that it becomes available for content authors. This process is essentially the same as publishing any item in MOSS. First the document is checked in, then it is published, and finally it is approved.

STEP 6: Create a New Page
Once the page layout is published and approved, content authors may use it to create new pages. This is done in the normal way by selecting the Create Page item from the Site Actions menu. After the page is created, the field controls may be edited to develop the actual page content.

Try a Question on Page Layouts

Or Try a Question on Page Layouts and Content Type

Anatomy of a Web Page displayed in MOSS

Today we will look how each page in Share Point is created. Each page is build with some basic components.
Each Published Page is based on a Layout Page. A Layout Page is based on a content type. Also these Layout pages references master page.
Following figure shows how the page layout and the Master pages are combined to create a web page in MOSS:
Master Page: A master page in a Share Point site defines the outer frame of each Web page. It determine the look and feel of the site. It contains the features, such as navigation links, that we want all pages in our site to share, and it provides a single place to control all of those features. Typically, a site uses a single master page, although large Internet sites might use more. For example, a corporate Web site that is used to publicize more than one product could use separate master pages so that the content for each product is properly branded. A master page is an ASP.NET file with the extension .master.
There are two types of master pages: site master pages and system master pages. The site master page is used on published Web pages in the site. It is the master page that site users and visitors see when they view published content. The system master page supplies the layout of pages in the site that implement the user interface for commands —for example, Document Library Settings.
Page Layout: A layout page is an Active Server Page Extension (ASPX) page that defines a layout for a type of content page. When a SharePoint site user opens a page in a browser, that page's associated layout page is first combined with the active master page, which supplies the outer frame of the page, and then the contents of the page are rendered in the fields (called field controls) on the layout.
We design layout pages to match the contents of a type of content page. For example, if a content page type has two images, the associated layout page should have fields in which to display both images. We can design multiple layout pages for the same content page. For example, for a page with an image, we may have one "image left" layout page and one "image right" layout page.
Content Place holder: The other core component that is used in a master page file are the Content Placeholders. A Content Placeholder is just that, a location flagged as where content will be inserted. The content is stored in the page layouts. The content placeholders designate where the content from the page layout will be inserted in the master page.
Content Placeholders can be wrapped in HTML code, for example DIV, SPAN or TABLE tags. A good way to think about it is everywhere we would place content that we would like to have customized for each page, insert a Content Placeholder.