Someone and somebody are both pronouns that are used to refer a person who is not known or specified. In most contexts, they are interchangeable. The only difference that most native speakers can agree upon is that someone is more formal than somebody (just as anyone is more formal than anybody, and everyone is more formal than everybody). This means that in a sentence like the one below, used in a legal context, someone is a much more likely choice than somebody. The bank requires that the deed be signed by someone authorized by the courts. It’s also interesting to note that someone is used more frequently than somebody, according to the data that we have on language use. http://www.learnersdictionary.com/qa/difference-between-someone-and-somebody

They are both the same meaning. Someone needs to teach me German. Somebody needs to teach me German.