This page helps you understand what the operations actually mean.
Did you know that subtraction is not always "take-away"? It can be comparison, completion, or missing addend. Click here for a chart showing the meanings of addition (3), subtraction (4), multiplication (4), and division (2).
More information on multiplication can be found at All About Multiplication.
More information on addition can be found at Do It with Dominoes.
More information on subtraction can be found at Comparing Connecting Cubes.