A while ago AI hadn't been complex and deep enough to warrant categories (especially to the layman), so it was just a general moniker put on everything from a smart piece of code with some adaptability all the way through to singularity level computer intelligence (as we'd imagine it). Now we're beginning to realise that there are vast ranges of categories out there, but it will take some time for consensus use to form (especially since a lot of them overlap into what we perceive as general intelligence, which we so far have had difficulty in defining and pinning down)