Quoting the official website:
The wwwroot folder is new in ASP.NET 5.0. All of the static files in
your project go into this folder. These are assets that the app will
serve directly to clients, including HTML files, CSS files, image
files, and JavaScript files. The wwwroot folder is the root of your
web site. That is, http://some.hostname/ points to wwwroot, all URLs for
static content are relative to the wwwroot folder.Code files should be placed outside of wwwroot. That includes all of your C# files and Razor files. > Having a wwwroot folder keeps a clean separation between code files and static files.
Source
It’s worth mentioning that the term wwwroot itself is certainly not new and it’s actually a convention used across many platforms (including J2EE applications and IIS itself with its c:\inetpub\wwwroot directory).
Similar conventions in the Unix/Linux world are htdocs, public_html and www.