The doc
command isn't specific to Play. Since play/activator wrap sbt, they inherit the sbt doc
command, which will generate scaladocs for all the source files in a project. Running it is pretty self explanatory. you'll see output like this:
[info] Main Scala API documentation to /path/to/project/target/scala-2.10/api...
And if you navigate to that directory, you'll see a bunch of generated html files containing the scaladocs for your project. So yes, it's generating html files, and yes it's meant for humans. Opening target/scala-2.10/api/index.html
will be much more telling.