Although all the races of the Whorl (except the Forged) derive from humans, the techniques used by the various gods to create them leaves them incompatible and infertile should they come to love members of another race. One of the two exceptions to this appear to be Elves and Humans who are, in rare cases, able to bear children encompassing traits from both races.
It is debated by scholars why this might be. Perhaps Surya, in creating the elves, sought to ensure that notwithstanding their immortality and commensurately long breeding times, they could still compete with the shorter-lived, more rapidly-reproducing humans. Whatever the cause, anywhere elves live in proximity to humans, there is bound to eventually be a small population of half-elves.
Half-elves derive physical features from their parents, as one might expect. This means that their variety in physical appearances is just as great as among humans, multiplied by the unique features of high elves, wood elves, and dark elves. As a result, there is little that can be usefully said that applies to them as a whole.