In English, we always need a subject. "It" is the gender-neutral subject used for things. For example: It is a beautiful day. The dog is annoying. It barks every day. (If we know the sex of the dog, we can use "he" or "she" as the subject. "Was" is the past tense of the verb "to be". It was a beautiful day. The dog was annoying. It barked all day.

it=eso / it was= era