VR stands for Variable Resistor
VR1 stands for Variable resistor number one in the circuit - it's also very probable that there is only one.
On your straighteners - you do not say the brand or the model - the VR may well be the little temperature wheel you can see in this video..
https://www.youtube.com/watch?v=KMLphjVT1XI
But that's just a guess...
Good luck..., May 2015
