this is intentional. there is also very little math.
this site looks at distributions visually
to develop an intuition about how they are related -
normally i am a big fan of labeling graphs and axes.
if you are curious about the math, check out the
code
that generated the data the site uses - you will also find some graphs with labels.
the probability density function ~ what values a random variable is likely to take for the distribution.
the gamma distribution shows up all over, with specific parameterizations being common distributions, and is used as a conjugate prior for a lot of distributions, so it's a good one to know.