The Odyssey book 19 notes

Odysseus tells Penelope his tale to give her hope. Penelope has been through a lot, and even though she stays faithful to her husband, she is beginning to lose faith in his promise that he would return. In telling her the story he is trying to help her keep her hope for a little bit longer.
Ereclyia plays an important role in that she realizes who Odysseus is when she sees the scar on his foot. It seems like she is a 'nanny' figure to Odysseus (or at least she was before he left) and a sort of 'helper' to Penelope while her husbend is away.