A computer from the late 80s/early 90s made by Commodore (of Commodore PET and 64 fame).
It was a direct competitor to the AtariST series and the Macintoshes which at the time ran on the same processor line, and indirectly a competitor to the Acorn Archimedes line, though these were primarily machines for the UK educational sector.
The Amiga line had;
A Motorola 68000 CPU @ 7.14MHz originally, the A500 did at least, as did the A500+ and possibly A1000 and others, later models (A600, A1200, etc) had higher M68k processors like the 68020 (A600/HD, A1200), 68030 or 68040 (A3000?), there were even multi-hundred-MHz expansion cards with highly clocked 68060s IIRC,
Between 512k and 2MB RAM usually, Sometimes you see them with more, but these tend to be production machines used by companies and video enthusiasts. Some games had issues with machines containing over 512KB or 1MB or RAM, some were even written to use the A500's CPU timing and as such were incompatible with later machines.
Didn't have a HDD, though the tower/desktop models did, as did the A600HD and the A1200 had the ability to have one, the A500's HDD would've been an add-on such as the GVP Impact series, though you could have up to 4 floppy drives (df0: df1: df2: df3:) on one machine, requiring you to daisy chain them from the external floppy port. The Amiga supported 880KB floppies usually (720K to you PC people, it had a different way of formatting the same disks) though higher capacity drives were later available, just like in PC-land.
Was popular for gamers, though was a good all-round machine, Commodore screwed up though so it's kinda long-dead now sadly. You can get an Amiga emulator called UAE (or WinUAE for Windows machines) which does the job of faithfully emulating the ol' dog.
PCs at this point couldn't match the Mac, the Amiga or the Atari in anything... graphics, sound, speed, usability... though they did soon catch up with VGA graphics, 8 bit ISA sound cards, joysticks, etc...