Often simply called 'workstation': a powerful synthesizer keyboard with sample-based synthesis, effects and sequencing capabilities built in. Other than that, today's workstations usually feature:
The first musical workstation in the modern sense was the 1988 Korg M1, which has become a modern classic by now; every other band seems to play one these days.
Well-known workstations available today:
Workstations of the past:
Musical workstations have become staples of nearly all on-stage and studio keyboard work in the pop and rock business; especially the pop business -- Britney Spears' backing band, for example, employs two keyboarders, each with a large Korg workstation (Triton or Trinity, I don't recall exactly) and several other 'boards. Don't confuse workstations with top-of-the-line arranger keyboards (a/k/a entertainer keyboards, portable keyboards, ...) such as the Yamaha PSR series which mainly serve one-man-band purposes and usually have built-in speakers. No self-respecting keyboard has built-in speakers. On the other hand, there are musical workstations without a real keyboard, i.e. groove boxes (note: Groovebox is a Roland trademark).