Zorro is the name of the peripheral attachment slots in the Amiga computers. It comes in three flavors Zorro (found in A1000 and A500), Zorro II (found in A2000) and Zorro III (found in A3000 and A4000).
As with all other parts of the Amiga the Zorro bus has a number features which was unusual at least at the time. From the start in 1985 the Zorro bus was totally self configuring, you plugged in any card you like and you were ready to fly. No tinkering with lousy jumpers to get that special irq that you needed, everything just worked when you turned the machine on. Zorro II was designed to emulate the bus of the Motorola MC68000 and was a lot faster than the first Zorro. A Zorro II card negotiates with the CPU for a piece of memory space in the Amiga to where all the card IO is mapped. Drivers will then use this memory space to control the card.
Zorro III was all designed by just one man, namely Dave Haynie the legendary Amiga engineer, cool impersonated. Quite a feat considering the competing PC standard at the time EISA had hundreds of engineers working on it. Zorro III is pin compatible with Zorro II, and Zorro III functioning is selected via a special bus signal. Zorro III is completely different from Zorro II. It is an asynchronous bus with bus time divided into two phases, an addressing phase and a data phase. It supports data bursts, bus mastering and quick interrupts to name a few. It is controlled (as is the Zorro II bus) by the custom chip called Buster.