Can a histogram have just one value as its bin in a probability histogram? On [this link], (http://www.henry.k12.ga.us/ugh/apstat/chapternotes/7supplement.html) there is a histogram where on the x-axis, all the sums of the two dice are there {2, 3, 4, 5, ... 12}, and on the y-axis, the probability that they will occur is there.
I thought histograms have to contain a range as their bin. Can someone help me understand this?
 A: 
I thought histograms have to contain a range as their bin.

This is not correct. Histograms show how many units fall into one of a finite number of bins, or what probability there is for an observation to fall into one of these bins.
Sometimes you already have a "natural" finite number of bins, as in the dice throwing example here: 11 bins. Then everything is straightforward.
However, sometimes you have too many bins to plot usefully, or even an infinite number of possible distributions, e.g., when the underlying distribution is continuous. Then, to build a histogram, you discretize the observations into a small number of bins, where every bin corresponds to a range of possible observations (where ranges should of course not overlap) - and then you proceed as above.
A: As the other answer here points out, it is possible to have a histogram where each bin is a single point (e.g., if we have a "natural" finite number of bins).  I will just supplement the other answer here by noting that in this case we usually would not call this a histogram at all (even though technically it is one).  Usually we would just refer to this as a barplot of the probability mass function.
