1. The document discusses the conjugation and use of the imperfect tense in Spanish. It explains how to conjugate -ar, -er, -ir verbs in the imperfect as well as the three irregular verbs ser, ir, and ver.
2. The imperfect is used to express actions that happened habitually in the past, ongoing actions and states without reference to beginning or ending, and mental/physical states. It can also be used to describe scenarios and situations in the past or express indirect statements.
3. Common uses of the imperfect include expressing age and time of day in the past, habitual actions, ongoing actions interrupted by other events, and setting the scene by describing multiple simultaneous past actions.