When a set contains only the elements of another set, that set is a subset of the other. Every set has at least one subset.
For example, set A: {1,3,5,7} is a subset of B because ALL elements in set A are found in set B.
set B: {1,2,3,4,5,6,7,8}.
Additionally, a set is always a subset of itself. Set A is a subset of set A. Set B is a subset of set B.
And the null set, {}, is a subset of every set. So {} is also a subset of set A and a subset of set B.