Mean absolute deviation means the mean distance of the numbers from their mean. It basically tells you how far are the numbers, on average, from the mean of the data.
Here is the video on how to calculate the mean absolute deviation on a calculator to accompany the notes.
Below is a shortened version of the directions from the video on finding the M.A.D.
The website here has a good explanation of how to find the M.A.D. by hand.