A perfect stub article is one which defines some context for the topic - a few short sentences describing what the page's intended for - but which doesn't go into too much depth. Even longer articles can be stubs, if the topic is complex enough to warrant it. Stubs are denoted by use of the stub template, which automatically includes them in the stubs category (this doesn't need to be done manually). Once an article has been expanded to no longer qualify as a stub, the stub template should be removed.
This article would currently qualify as a stub.