What is a 'gas constant'?
It is a proportionality constant that relates Pressure and Volume to the Temperature and number of moles of a gas.
If you think of a circle, then it has a circumference and a radius. The circumference and radius are related to each other by a proportionality constant called
It is the same idea for gases. For a gas, its pressure, volume, amount, and temperature are all related to each other by a constant called the Gas Constant.
PV=nRT is the ideal gas law equation, and if we rearrange, we see that R = PV/nT
That means that the ratio of the pressure and volume of a gas to the amount of that gas and the temperature is a constant.