For example, let's say we are given: "I saw Sally yesterday. She was lying on the beach". Here "she" is an endophoric expression because it refers to something already mentioned in the text, i.e. "Sally".
By contrast, "She was lying on the beach," if it appeared by itself, has an exophoric expression; "she" refers to something that the reader is not told about. That is to say, there is not enough information in the text to independently determine to whom "she" refers. It can refer to someone the speaker assumes his audience has prior knowledge of or it can refer to a person he is showing to his listeners. Without further information, in other words, there is no way of knowing the exact meaning of an exophoric term.