"era" y "fue" corresponden a diferentes tiempos del Modo Subjuntivo en español. "era"= es el verbo "ser" conjugado en el Pretérito imperfecto del Modo Indicativo: Yo era, Tú eras, Él / ella era, Nosotros éramos, Ustedes eran, Vosotros erais, Ellos / ellas eran. "fue" = es el verbo "ser" conjugado en el Pretérito perfecto simple del Modo Indicativo: Yo fui, Tú fuiste, Él /ella fue, Nosotros fuimos, Ustedes fueron, Vosotros fuisteis, Ellos / ellas fueron. Como Usted puede ver, los tiempos de conjugación son diferentes, como también la perfecta aplicación de su uso será diferente de acuerdo a lo que se quiera expresar.

era, eramos.....is "USED TO BE" which is used to describe a situation that happened simultaneously with another, or when there's a change in the circumstances. El ERA EL MAS JOVEN. He used to be the youngest, which indicates that he no longer is. JOSE ERA JUGADOR DE FUTBOL CUANDO ESTUDIABA LA PREPARATORIA -- Jose used to be a football player when he was in high school. YO ERA MUY BUENO EN MATEMATICAS -- I used to be very good at math --- but this means I no longer am. VERONICA Y YO ERAMOS AMIGAS -- Veronica and I used to be friends -- but not anymore. Mnd you, you could also use FUIMOS in this case, cuz it's something that started and ended in the past. But in the other cases you do have to use era, eramos, etc. FUI / FUE / FUIMOS....... is the past tense of the verb TO BE or TO GO. TO BE ...... "El fue estudiante de este instituto en 1990": he was a student at this institute in 1990. "ellos fueron perseguidos por la policia": they were chased by the cops. This is used for an action which happened (and ENDED) in the past. The guy is no longer a student there..... and "they" were chased by the police yesterday, last month or last year, but it's over. ALSO SEE http://spanish.about.com/cs/verbs/a/serpast.htm HOPE IT HELPS.