Website Builder is now Websites in the sidebar, on the Dashboard and in Help. The name covers both kinds of website the area holds: an editor website, built from sections and pages, and a files website, made of files you upload or push to a repository.
New website on the Websites page asks for a name and how the website is made, and makes its address from the name; the address can be changed afterwards. Nothing about your existing websites changes, and /websites is still the address.