Given the sets $A = \{1, 2, 3\}$ and $B = \{1, 2\}$, let's find the following:

1. $A \cup B$ (A union B):
   The union of sets $A$ and $B$ contains all elements from both sets without duplication.
   $A \cup B = \{1, 2, 3\}$

2. $A \cap B$ (A intersection B):
   The intersection of sets $A$ and $B$ contains only the elements common to both sets.
   $A \cap B = \{1, 2\}$

3. $A - B$ (A minus B):
   The set difference $A - B$ contains elements that are in $A$ but not in $B$.
   $A - B = \{3\}$

4. $B - A$ (B minus A):
   The set difference $B - A$ contains elements that are in $B$ but not in $A$.
   $B - A = \emptyset$ (no elements are in $B$ that are not in $A$)

5. $A \Delta B$ (A symmetric difference B):
   The symmetric difference of sets $A$ and $B$ contains elements that are in either $A$ or $B$ but not in both.
   $A \Delta B = \{3\}$

Let me know if you need further details or have any questions!

Here are some related questions to explore:

1. What is the union of three sets?
2. How does the symmetric difference relate to union and intersection?
3. How do set operations change when dealing with infinite sets?
4. Can the intersection of two sets ever be larger than either set?
5. How do the properties of $A \cup B$ and $A \cap B$ change if $A \subseteq B$?

Tip:
The symmetric difference $A \Delta B$ can also be expressed as $(A - B) \cup (B - A)$.