Nerwicks are a fictional species present in this story. Popular Nerwicks in the Harry Potter series include:
People with all the qualities of Nerwicks are also called Wickens, though there are many other, more derogative terms.
Nerwicks can be easily mistaken for humans but there are a few key differences, the most obvious being their ears. Most elven myths are loosely derived from Nerwicks as their ears are as pointy as those of Santa's little workers. They are also rather scrawny, though there are exceptions, they have big eyes and their blood is blue.
Old folk tales say this is because Nerwicks spend so much time near the sea and became pirates, stealing away human women and taking the captain's treasure. Consequently, the sea god cursed them with blue blood, presumably to warn the innocent of their cold-heartedness. However, these tales hold no weight today and are tossed aside as fiction.
I do believe that covers most Physical differences.
Like humans, some Nerwicks are magical and some aren't, but unlike humans, most of them are told of the existence of magic. There are of course, exceptions, like if a Nerwick is human born and the humans decide to keep them, they will probably not be told of magic. Speaking of human born, yes, Nerwicks can be produced by two humans. It is rare, but it does happen and as far as modern science goes, there is no explanation.
Historically, Nerwicks borne from to humans are kept secret and killed. Such was the regular practice until 1950, when a law was passed to prevent it and ensure the children either stayed with the parents or sent to live with willing Nerwicks.
The Nerwicks are also very deeply religious people. They believe in a singular God, but many angels. These angels are limitless, and there is an angel for everything from the sun and shoes to more abstract things like music and greed. Names of these angels are disputed among the Nerwicks and so are usually referred to as Angel of (insert thing the angel is associated with). Everyone, however, agrees that there is a God ruling over them all.
There are no atheist Nerwicks, just like there aren't any Muslim Jews. It's a contradictory thing, as being Nerwick and believing in the Nerwick religion come in one package. You can't have one without the other.
The most widely known thing about Nerwicks, though, is not their appearance, their religion or their name, it is the bigotry that surrounds them. They are just about the only thing Wizards and Muggles agree on, whether they know it or not. Throughout history, Nerwicks have been at everlasting war with humans, magic and muggle alike. They have been oppressed and they have revolted time and time again. In the brief moments of peace, they are not given the same rights and aren't permitted in the same schools as humans.
They have remained vigilant still, and let it not be said that humans are careless by nature as many have sympathized with their plight and done their best to aid these poor creatures. In fact, as of 1950, a decree was passed in the Ministry of Magic that allowed magical Nerwicks to receive their magical education in Hogwarts instead of the standard apprenticeship they usual receive and since then, tensions have lightened dramatically.
You might have noticed that 1950 was a very special year for the Nerwicks, and indeed, you are correct in assuming so. However that is a story for another time, yet you can be certain it includes a certain raven-haired green eyed wicken.