Estar (imperfecto) vs imperfecto itself

Question

Hello! Could you tell me if tehre is any difference between "estar (imperfecto) + gerundio" and "preterito imperfecto"?

"Estaba cantando"

vs

"Cantaba"

Can we use them interchangeablely?

EDIT: I've read that "estar (imperfecto) + gerundio" and "estar (indefinido) + gerundio" are similar to English past progressive. Is it true?

Thanks

(This was already answered here)[http://www.spanishdict.com/answers/285494/vena-agarrando-vs-agarraba#a927153]. - Oshnaj, Aug 13, 2016

This has been answered. Please do not post twice. - rac1, Aug 13, 2016

My answer is different from what was given. I usually give my answer from the "English speaker's" view, instead of the hispanohablante. The latter is sometimes difficult for an English speaker to grasp. - Daniela2041, Aug 13, 2016

Answer 1

The past (or imperfect) progressive is used to STRESS that something was going on.

(yo) Estaba comiendo tacos. Means only I WAS EATING tacos, whereas "comía tacos can mean I was eating tacos" or "I used to eat tacos." (plus several more meanings, but I don't want to confuse you here.)

That is precisely my understanding. Thanks. :) - bosquederoble, Aug 13, 2016

Pero tu me ha confundido ahora. ;) - ray76, Aug 14, 2016

¡Una respuesta excelente, amiga ...es muy fácil entender todo lo que has escrito! ;) - FELIZ77, Aug 14, 2016

Gracias, mis amigos. - Daniela2041, Aug 14, 2016