1. The problem is to explain **"A and B" for sets** with a simple example, not a general rule. 2. For sets, **"A and B"** usually means the **intersection**, written as $A\cap B$. 3. The formula is: $$A\cap B=\{x \mid x\in A \text{ and } x\in B\}$$ 4. Important rule: an element must be in **both** sets to belong to the intersection. 5. Example: let $A=\{1,2,3,4\}$ and $B=\{3,4,5,6\}$. 6. Check which numbers are in both sets: $3$ and $4$ are in $A$ and also in $B$. 7. So the intersection is: $$A\cap B=\{3,4\}$$ 8. Final answer: **"A and B" means the elements common to both sets, and for the example above, $A\cap B=\{3,4\}$**.