This document provides an overview of Spanish grammar concepts including:
1) The preterite tense is used for completed past actions with a definitive start and end. Regular verb forms and common irregular verbs are discussed.
2) The imperfect tense describes ongoing or habitual past actions and includes information on its usage and irregular verb forms.
3) The difference between the preterite and imperfect tenses is explained, noting that the preterite conveys specific events while the imperfect provides background context.