I think you mean "median" The median is the exact middle of all the data (not the average). So, if you have a dataset of (1, 4, 7, 10, 15, 22, 23), then the median in this case would be 10, because 10 is the exact middle of the data set.
If you had an even number of elements in the dataset then you average the middle 2 numbers. So, if you hvae a dataset of (2, 4, 6, 7, 11, 34), then the median would be the average of 7 and 11. (7 + 11)/2 = 18/2 = 9. So the median in this dataset is 9.