C # How to Use masterpage on a webpage

What is masterpage? I think it is a template that makes the same part of different webpages, such as the navigation bar, logo, page header, and footer into a masterpage, which reduces the workload and does not need to maintain a setCode. Nonsense:

1. Create a masterpage page in Vs, add new item, and add masterpage, as shown in:

2. layout in masterpage. Note that contentplaceholder allows other pages to place their own controls. We only need to put each webpage public,

3. Create a page and select "select master page ",

OK.