# In the equation PV=nRT, what does the R and n stand for?

Well, $n = \text{number of moles}$
And thus $n$ is equal to the number of gaseous particles....i.e. which we express in units of moles. And $R$ is the universal gas constant. There are several expressions for $R$.. For chemists, possibly the most useful one is $R = 0.0821 \cdot L \cdot a t m \cdot {K}^{-} 1 \cdot m o {l}^{-} 1$; chemists routinely deal with litre volumes, and gram quantities, and express pressure in units of atmosphere...