The usual rules of multiplication is that multiplication is "commutative", in other words the order of the multiplication does not matter. Two numbers, example 12 and 14 will multiply together to produce 168, similarly reversing the numbers will produce the same result. 


This property makes multiplication (and addition) commutative.


With matrices this does not always apply. Two matrices A and B may multiply together to produce a product AB or BA but it does not necessarily follow that the result  AB = result BA.




If we multiply matrix A and matrix B:


However, multiplication of matrix B and matrix A: