what is the function of webpages:Enabled in MVC 3 web.config

webPages:enabled with value false prevents .cshtml or .vbhtml files in the Views folder from being directly accessible from a web browser.

According to documentation it prevents .cshtml and .vbhtml files from being accessed directly (www.myweb.com/views/home/index.cshtml for example)

To allow Razor pages to be served, it's not enough to set <add key="webpages:Enabled" value="true" />. You also need to add the Microsoft.AspNet.WebPages package to packages.config using NuGet.