“Said” is a more general word. It applies to any words that come out of a person’s mouth. “Told” is more limited: it applies when (i) a person is giving an order (e.g., “The mother told her children to go to bed.”) or (ii) a person is teaching, instructing, or otherwise relaying information to another person (e.g., “The teacher told the students about World War I.” Or “He told me that he was born in Australia”).