1. **Problem:** Draw a Venn diagram for a set union with an example. 2. **Rule for union:** The union of two sets, written as $A \cup B$, includes everything that is in $A$, in $B$, or in both. 3. **Example sets:** Let $A=\{1,2,3\}$ and $B=\{3,4,5\}$. 4. **Find the union:** $$A \cup B = \{1,2,3,4,5\}$$ 5. **How to read the diagram:** The left circle is set $A$, the right circle is set $B$, and the overlap shows the common element $3$. 6. **Final answer:** The union is all elements from both sets, so the shaded region would cover both circles including the overlap.