In SharePoint we have 2 types of pages.
- Site Page
- Application Page
Site
Page:
- Site Pages are Site or Web Scoped.
- User can customize Site Pages.
- Site Pages is a concept where complete or partial page is stored within content
database and then actual page is parsed at runtime and delivered to end-users.
- There is no custom code in Site Pages.
- Site pages can be edited by using SharePoint Designer tool.
- Site Pages are Un-ghosted Pages
- Site pages are used within Sandboxed solutions.
Application
Page:
- Application Pages are farm scoped
- Application pages are stored in the server's file system.
- SharePoint Designer tool cannot be used with application pages.
- Application pages cannot be used within sandboxed solutions.
- No customization can be done by the user.
- Application Pages are stored in _layouts
folder
- There is custom code in your Application
Pages.
- Application Pages are Ghosted Pages.
- Since application pages are compiled once, they are much faster.
Now here we will learn how we can add a new Application
Page and how we can show this in SharePoint Site.
In your Visual Studio solution -> Right Click ->
Add New Item-> Add an Application Page
Now Right click on your solution -> Deploy

Image 1.
After Successfully Deploy check your page in 14 hive
directory.

Image 2.
Now open your SharePoint Site -> Site Actions ->
Site Settings -> Look and Feel -> Top Link Bar.

Image 3.
Click on new Navigation Link.

Image 4.
Here give the path of your Application page and Name
-> Ok.

Image 5.
Now click on Link and see your application page:

Image 6.