Well, Ami, I suppose functional parents are "good enough" parents. It is not easy to describe. Parents, like all humans, have their faults and failings. Everyone can have a bad day, for one reason or another. The difference is that with N parents, or otherwise abusive, non-nurturing parents, that their "condition" is all-pervasive, ingrained, and sad to say, permanent.
A good parent resonates with the child, gives encouragement, is just and fair (a parent can be strictish, but just at the same time). A good parent has to try to be consistent, (dysfunctional parents will yell at the child, strike out, then the next day maybe smother the child with something that passes as "love", or gives some object as a kind of "peace offering", or whatever). A good parent does not do that. Also, good parents are able somehow to keep a light hand on the reins, giving just enough to the child to keep going, to progress. A good parent, even if she or he lets a yell at you once in a while, you know it is not in bad faith, and that all is essentially well.
An example: my brother, not long after he learnt to drive, turned Dad's car over because somehow he just didn't have the experience to handle a sudden hump in the road. The car was really a write off, but my brother was unhurt. Dad did not say a word, except to remark: "thank goodness he is all right. that is the main thing." Dad (who probably did get a fright himself at the news), might have wanted to go mad, to jump up and down, rage, demean, but being a normal sane person he did not do that.
There were two things Mum and Dad were very very strict about: one was lying, the other was stealing. We were warned never ever to touch a coin even, that might be left on a shelf, or in the kitchen or wherever. However, if we asked for that coin, we would no doubt be given it, or perhaps we would do some little errand to "earn" it. If you owned up to some misdemeanour, you might get a bit of a telling off, but we were not punished. But lying, in any shape or form was out of the question. So, we never lied.
I always loved reading, and Dad encouraged this, and there were never any censorship placed on what I read.
He was a well-travelled and well-read man himself, and he wanted us to look outwards as much as possible.
I often think of the huge amount of patience my Dad showed. I know, and found out in later life about all the other parents he encouraged to do the best for their kids. He said kids needed a good start in life. For him that was paramount.
All the best
Hermes