A VRB (Visual Response Boost) is a feature that reduces blurring in fast-moving images to achieve a 1ms MPRT (Moving Picture Response Time).
Basically, if you enable VBR on that monitor, you’ll get a 1ms response time.
However, IPS monitors can’t get faster than 4ms GTG (Grey to Grey) because of the design of the IPS panel. In order to get the 1ms response rate, monitor manufacturers, like Acer, use different technologies (MPRT, VRB, etc.).