In Neo4j, vertices are called nodes. Nodes can be of different types, like Question and Answer were in our former example. In order to differentiate those entities, nodes can have a label. If we continue the parallel with SQL, all nodes with a given label would be in the same table. But the analogy ends here, because nodes can have multiple labels. For instance, Clark Kent is a journalist, but he is also a superhero; the node representing this person can then have the two labels: Journalist and SuperHero.
Labels define the kind of entity the node belongs to. It is also important to store the characteristics of that entity. In Neo4j, this is done by attaching properties to nodes.