Debian typically uses code names to refer to its releases, starting with the Toy Story character names used (mostly) instead of numbers. The "Buster" release is due on July 6 and you will rarely hear it referred to as "Debian 10". There are some other code names used for repository (or suite) names in the Debian infrastructure; "stable", "testing", "unstable", "oldstable", and sometimes even "oldoldstable" are all used as part of the sources for the APT packaging tool. But code names of any sort are hard to keep track of; a discussion on the debian-devel mailing list looks at moving away from, at least, some of the repository code names.