Kurtosis is the degree to which the frequency distribution is concentrated around a peak, that is, it describes the sharpness of the central peak of the curve, usually as compared with the normal distribution.
Higher kurtosis means more of the variance is due to infrequent extreme deviations (more variance, less concentrated around the mean), as opposed to frequent modestly-sized deviations (less variance, more concentration around the mean)
The normal distribution is mesokurtic; the curve with a higher degree of kurtosis (peakedness) is leptokurtic; and the curve with the flat top (compared to the normal curve) is platykurtic.
Links:http://www.riskglossary.com/articles/kurtosis.htm
http://mvpprograms.com/help/mvpstats/distributions/SkewnessKurtosis
http://www.statistics4u.info/fundstat_eng/cc_kurtosis.html
