Verbs are conjugated to show tenses, of which there are two: past and present (or non-past) which is used for the present and the future. For verbs that represent an ongoing process, the "-te iru" form indicates a continuous (or progressive) aspect, similar to the suffix "ing" in English. For others that represent a change of state, the "-te iru" form indicates a perfect aspect. For example, "kite iru" means "He has come (and is still here)", but "tabete iru" means "He is eating".