The ResolveUrl method is designed to create a friendly URL for a given
resource. For example, when you have a control that references an image,
you'll want the image to be referenced correctly when that control is placed
within a page. The ResolveUrl will create the url in a friendly way that is
relative to the page instead of relative to the control.
The Server.MapPath is used to find the file system path for a given
resource. For example: Server.MapPath("web.config") may give something like
c:\inetpub\wwwroot\web.config. It's used when you're trying to work with
files from the server's file system, such as saving uploaded files, creating
files on the server, referencing file-based databases.
