That would have been a specific machine built around the Z80. The Z80 CPU has a 16-bit address bus and can handle 64K of memory. It has an 8-bit I/O bus, but it was common for Z80-based machines to use memory-mapped I/O like the 6502.
Two very common machines from the era were the ZX spectrum and the TRS-80. But there were dozens - Kaypro, Osborne, MSX, the Nintendo Gameboy... the Z80 was used in lots of machines. Chips based on the Z80 are still used in embedded systems today.
I built a retro-computer this year using a Z180, which is a Z80 (minus undocumented behaviours) core with a handful of useful peripherals built in. They're still actively manufactured and sold.
The Gameboy did not use the Z80. Gameboy CPU was derived from the 8080 with a smattering of Z80 instructions (very few in the big picture). However, the Sega Master System was a full on Z80.
Two very common machines from the era were the ZX spectrum and the TRS-80. But there were dozens - Kaypro, Osborne, MSX, the Nintendo Gameboy... the Z80 was used in lots of machines. Chips based on the Z80 are still used in embedded systems today.
I built a retro-computer this year using a Z180, which is a Z80 (minus undocumented behaviours) core with a handful of useful peripherals built in. They're still actively manufactured and sold.