The expression in the image is the union of set $\emptyset \cup \emptyset$, which denotes the union of the empty set with itself.

The union of two sets, $A \cup B$, consists of all elements in either $A$ or $B$ (or both). Since both sets here are empty (denoted by $\emptyset$), there are no elements to include in the union. Therefore:

$\emptyset \cup \emptyset = \emptyset$

Thus, the result of this expression is $\emptyset$, meaning the union of the empty set with itself is still an empty set.

Would you like further details or have any questions?

Here are five related questions for further exploration:

1. What is the difference between the union and intersection of sets?
2. How does the union operation behave with sets that are not empty?
3. Can you explain the concept of a universal set in set theory?
4. What happens when you intersect an empty set with any other set?
5. Why is the empty set considered a subset of all sets?

Tip: The empty set, denoted $\emptyset$, is unique in set theory and serves as the identity element for union operations with respect to itself.