"Era" comes from the Spanish verb "ser" = "to be." It is in the personal form and it is conjugated to serve in the first person [Yo, which translates to English as "I"].
Curiously, it also serves in the third person for (he, she or it [el, ella, eso]making no distinction in the way it is spelled out).
Having that in mind, now, let me explain how "era" is used. It roughly translates to English as "I used to be or he/she/it used to be) depending on the context. Keep in mind Spanish speakers not always necessarily specify which person we refer to since it's already given by the way the verb is conjugated and implied in context.
One example could be [in this case I'll use the personal pronoun]
"Yo era muy flaco" I used to be really skinny.
Another example, could be:
"Mi gato era muy activo" My cat used to be very active.
However they are cases in which it gets confusing, like
"Era muy temprano" It used to be real early"
On the other hand "fue" originates from the Spanish verb "ser" = "to be" but it is in the past tense form (ONLY in the form of the third singular person). "They" is not included.
Fue" is translated to English as "he/she/it was"
Keep in mind that the verb "ser" is one of the most complex to learn as it requires to make the distinction between something permanent and something temporary.
For example "fue" is the past tense of what you could think as a permanent condition. Something like, a person who throughout his life was very tall. It cannot be changed, the color of the eyes, etc.
El fue muy alto = He was very tall.
Things like He was very tired, are only temporary and CANNOT be described with the verb "ser". You have to use another verb, for temporary "estar"
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"Era" comes from the Spanish verb "ser" = "to be." It is in the personal form and it is conjugated to serve in the first person [Yo, which translates to English as "I"].
Curiously, it also serves in the third person for (he, she or it [el, ella, eso]making no distinction in the way it is spelled out).
Having that in mind, now, let me explain how "era" is used. It roughly translates to English as "I used to be or he/she/it used to be) depending on the context. Keep in mind Spanish speakers not always necessarily specify which person we refer to since it's already given by the way the verb is conjugated and implied in context.
One example could be [in this case I'll use the personal pronoun]
"Yo era muy flaco" I used to be really skinny.
Another example, could be:
"Mi gato era muy activo" My cat used to be very active.
However they are cases in which it gets confusing, like
"Era muy temprano" It used to be real early"
On the other hand "fue" originates from the Spanish verb "ser" = "to be" but it is in the past tense form (ONLY in the form of the third singular person). "They" is not included.
Fue" is translated to English as "he/she/it was"
Keep in mind that the verb "ser" is one of the most complex to learn as it requires to make the distinction between something permanent and something temporary.
For example "fue" is the past tense of what you could think as a permanent condition. Something like, a person who throughout his life was very tall. It cannot be changed, the color of the eyes, etc.
El fue muy alto = He was very tall.
Things like He was very tired, are only temporary and CANNOT be described with the verb "ser". You have to use another verb, for temporary "estar"
El estuvo muy cansado = He was very tired.
You can find a complete list of all the conjugations of verbs like ser at http://www.rae.es/rae.html
Type in verb and "conjugar"
YO ERA would be I WAS
and EL FUE/YO FUI would be HE WENT/I WENT