The preterite is a simple past tense form generally expressing an action as being 'delimited' in time. (In contrast, the imperfect generally expresses an 'non-delimited' event or state.) The Spanish preterite is often the equivalent to English simpe past tense forms such as did, hit, decided, said etc.
In written Spanish, many common preterite forms are third person singular ("he/she/it") forms of -ar verbs. These forms end in -ó:
Other verbs can have various irregularities in the preterite, such as vowel changes in the stem and a variety of endings. Common irregular, preterite forms include fue from ser ("he/she/it was") and estar (estuvo).