This paper deals with new descriptive statistics for histogram data, in the framework of symbolic data analysis. A main contribution consists in defining the main order statistics (median and quartiles) of a histogram variable using the quantile functions associated with the corresponding empirical distribution functions of the observed histograms. The definition of an order relationship between quantile functions is based on an appropriate probabilistic metric: the `p Wasserstein distance. Starting from the median and quartile functions definition, we extend the classic box-plot representation for set of quantile functions. Finally, we propose new measures of variability and skewness for a histogram variable associated with this representation. An application on real data allows us to corroborate the proposed measures and the new box-plot visualization tool.