The below examples assume a N(0,1). A link to the R manual is here.
dnorm-returns the height of the normal curve at a specified value along the x-axis
qnorm-returns quantiles or "critical values"
rnorm-generates random numbers from the normal distribution
These are examples for the normal distribution, but as you could imagine R has commands for numerous other distributions such as the chi-square, beta, uniform, and poisson.
If you are curious, here are the commands I used to plot these figures: