A video terminal was a device used to allow a user to do input/output to a computer; it usually communicated with the computer via asynchronous serial line. It was effectively roughly the same as the earlier printing terminals such as Teletypes, but with characters being 'painted' on a CRT via a purely electronic proces, instead of being printed on paper by a mechanical system.
The original chief advantage was speed, since the all-electronic mechanism could run at much higher speeds; the disadvantage was that only a limited amount of information could be displayed at one time.
Very early model provided only the same motion controls as their printing predecessors - line feed, carriage return, etc. However, the ability to go to specific screen locations was soon added, which made possible a predecessor of WYSIWYG, to wit, screen editors such as EMACS.