Latency is a major factor in a good VR experience. Latency refers to the time that passes between an action happening and the display updating to reflect this. An example would be the user moving their head and having the world around them immediately show this or controllers moving in the VR space which exactly matches the movement in the real world.
This time gap is usually tolerable in traditional video games on monitors or TV screen. In VR it can cause significant issues which can be immersion-breaking and also lead to VR sickness.