What are the relationship between set?

Answer 1

Two sets A and B can be joined together with A U B. This would be all the elements in both sets. If A = {a,b,c} and B = {x,y,z} then A U B = {a,b,c,x,y,z}.

Two sets A and B can intersect (the symbol is an upside down U). In the above example, the intersection of A and B is the empty set, because they have no common members. As an example where they do have some common members, let A = {a,b,c,d,e,f} and B = {e,f,g,h}. Then A intersect B = {e,f} because those are the members common to both.

Also, a set can be contained within another set. The containment symbol looks like a C with a line drawn under it. Let A = {a,b,c,d,e,f} and let B = {b,d,f}. Then B is contained within A, i.e., B C A. (Sorry. You'll have to imagine the line under the C.)