In either case, the distributive property can be described in words as:
If the operation outside the parentheses (in this case, the multiplication) is commutative, then left-distributivity implies right-distributivity and vice versa, and one talks simply of distributivity.
One example of an operation that is "only" right-distributive is division, which is not commutative:
Multiplying sums can be put into words as follows: When a sum is multiplied by a sum, multiply each summand of a sum with each summand of the other sum (keeping track of signs) then add up all of the resulting products.
The distributive law is valid for matrix multiplication. More precisely,