Despite having similar translations in English, tener and haber serve very different purposes in Spanish. Tener is used to express possession or ownership of something, for example having a car or having siblings. In contrast, haber is used as an auxiliary verb to form compound tenses, such as the present perfect (he comido - I have eaten) or past perfect (había terminado - I had finished). While tener can be used as a main verb with direct objects, haber must always be followed by a past participle and cannot express possession.