Spanish has two "simple" past tenses, the preterite and the imperfect. "Estuve" uses the preterite, while "estaba" is an example of the imperfect. You use the preterite (estuve) when you talk about something that happened once or that happened more than once but had a specific end, whereas you use the imperfect (estaba) for habitual or repeated actions. Some examples: Estaba (non-specific range of time): "I was in the kitchen" = "Yo estaba en la cocina" "I was sad" = "Yo estaba triste" Estuve (specific range of time): "I was in the kitchen this morning" = "Yo estuve en la cocina esta mañana" "They were here" = "Ellos estaban aqui" "They were here last night" = "Ellos estuvieron aqui anoche"

The verb "to be" in Spanish has two variants: "ser" and "estar". "Ser" is understood as a permanent condition and "estar" as a temporary condition. For example: Ella está enferma ("está" from the verb "estar") she is sick (but she will recover). Ella es enferma ("es" from "ser") she is sick (chronically). Spanish has two forms of past, "perfective" and "imperfective". "Perfective" means that the action has limits (this should not be confused with "complete or finished actions"). And the "imperfective" past indicates that the action lasted for a certain period of time or it was a habitual action. For example: Cuando yo era pequeño VISITÉ a mi padre (perfective) = when I was a kid I visited my father. Cuando yo era pequeño VISITABA a mi padre (imperfective) = when I was a kid I used to visit my father. Perfective past of "ser" Yo fui Tú fuiste Él fue Nosotros fuimos Ustedes fueron Ellos fueron Imperfective past of "ser" Yo era Tú eras Él era Nosotros éramos Ustedes eran Ellos eran Perfective past of "estar" Yo estuve Tú estuviste Él estuvo Nosotros estuvimos Ustedes estuvieron Ellos estuvieron Imperfective past of "estar" Yo estaba Tú estabas Él estaba Nosotros estábamos Ustedes estaban Ellos estaban. I hope this answers your question.