Histogram
Histogram are column-chart, where each column represent a range of Value
To make a Histogram , the data is stored into bins and the number of data point in each bins is counted.
The height of each column in the histogram
is then proportional to the number of data points its
bin contains.
The df.plot(kind=’hist’) function automatically selects
the size of the bins based on the spread of values in
the data.