In everyday language the word average refers to the value that in statistics we call arithmetic mean. So for example if the IQs of the people in your family are. So if the numbers that you have are 3 7 8.
In statistics there is no difference between the mean and average.
In general you calculate the mean or average of a set of numbers by adding them all up and dividing by how many numbers you have. Before we get to the real estate specific examples lets quickly review the definition of each term. So for example if the IQs of the people in your family are. So the rounded average or mean score is 74.