How is Telemachus' journey important for both him and Odysseus?

Athene advises Telemachos to go to travel to Sparta to find news about Odysseus from Nestor and Menelaos. In Pylos Telemachos talks to Nestor who tells him that Athene really favors Odysseus. Then he travels to Sparta to see King Menelaos. The King tells Telemachos that Odysseus is still alive and can't get off Kalypso’s island.