Oops. They have mistakes in that article! For example - "Synthesizers or samplers that have percussion and rhythm sounds fall in the workstation category". That's not true. Most synths, if not ALL synths have percussion sounds. That does not make them workstations. Workstations are those with build in sequencers hence making them an all-in-one keyboard as opposed to a pure synth which do not have a build-in sequencer. They used the term "sampler" as if they don't really know the meaning of it.
They also did not include digital pianos, stage pianos etc.
But nevertheless, a nice little article as an intro.