It had a white plastic case, a touch membrane keyboard, 1KB RAM, BASIC available on 4K of ROM, black and white video output to TV, with no graphics mode. It kickstarted the 80s home computer craze in the UK for people who could solder or had friends that could.
The video display generator of the ZX80 used very minimalistic hardware, plus a combination of software to generate a video signal. As a result of this approach the ZX80 could only generate a picture when it was waiting for a key to be pressed. When running a BASIC program the display would black out. This prevented moving graphics etc. The later ZX81 improved on this somewhat because it could run 'slow' while creating a video signal, or 'fast' without generating a video signal.
It was the precursor to the ZX81 and ZX Spectrum.