Tú recibiste una tarjeta postal. This means: you received a postcard. Recibiste is the preterite of the verb recibir in the second person of the singular.
Ustedes bebieron un café. This means: You drunk coffee. Bebieron is the preterite of the verb beber in the second person of the plural.
Yo comí la torta. In English this means: I ate the cake. Comí is the preterite of the verb comer in the first person of the singular.
Yo subí por la escalera. This means I went up the stairs. Subí is the preterite of the verb subir in the first person of the singular.
