Preterite indicates a single event ( something that you dosen't do so often )
the imperfect indicates something that you do habitual
Mi mama es la persona mas trabajadora de la familia.
"Mama" (mom) can be replaced by the pronoun "ella" (she). The correct conjugation for "ser" in the el/ella/usted form is "es".
Hope this helps!!
Last and first one are true
Pobrecita means poor thing
