Most distributions in R have densities, cumulative densities, quantiles, and RNGs. They are generally called in R using the same approach (d for densities, q for quantiles, r for random numbers, and p for the cumulative density function) combined with the distribution name.

For example, qnorm returns the quantile function for a normal-Gaussian distribution, and qchisq returns the quantile function for the chi-squared distribution. pnorm returns the cumulative distribution function for a Gaussian distribution; pt returns it for a Student's t-distribution.

As can be seen in the diagram immediately previous, when we get the 97.7% quantile, we get 1.99, which coincides with the accumulated probability we get when we do pnorm() for x=2.