Vocabulary - Intersection

The intersection of sets $A$ and $B$ is the set of elements that belong to both $A$ and $B$. You write $A \cap B$.

For example, if $A = \{1, 2, 3\}$ and $B = \{2, 3, 4\}$, then $A \cap B = \{2, 3\}$. Only $2$ and $3$ appear in both.

If two sets share no elements, their intersection is $\emptyset$. In code, intersection finds common items between two collections.