The capital "N" is the notation for a normal distribution. The first parameter mu denotes the population mean. The second parameter is usually the population variance, but from the sigma Greek letter you used, it appears to be the population standard deviation.
Answers & Comments
Verified answer
The number N of items in the set
The mean value µ of the items (the arithmetical average)
The standard deviation σ of the data set (how scattered the data are)
The capital "N" is the notation for a normal distribution. The first parameter mu denotes the population mean. The second parameter is usually the population variance, but from the sigma Greek letter you used, it appears to be the population standard deviation.