If i understand it correctly "есть" is used to indicate the existence of something. Since we didn't know the park existed before, "есть" is necessary.
So from what I understand: without есть would be "The park is near the house." With it, it's "There's a park near the house."
Does it roughly translate to "in the vicinity/neighborhood of the house there is a park"?
'There is a park by the house' is marked incorrect but I don't understand why.