What is the difference between a night elf and a blood elf?

Answer 1

Yes,

Drow elves by definition are The drow (pronounced either IPA: /ˈdraʊ/, rhyming with "now",[4] or /ˈdroʊ/, rhyming with "throw," per Mentzer, 1985[5]) or dark elves are a generally evil, dark-skinned subrace of elves in the Dungeons & Dragons fantasy roleplaying game.[2]

Night elves, or kaldorei ("Children of the Stars" in their native tongue of Darnassian), have a long and fascinating history. Native to the western continent of Kalimdor, the night elves ended a long period of seclusion at the end of the Third War and became members of the Alliance.

Answer 2

Physically Night Elves have more color in their skin, slightly longer ears and look a bit more physically fit while Blood Elves look more "humanish" with normal skin tones.

Night elves are more into nature, shying away from the arcane magic (except for the recent addition of mages to the Night elf classes), while Blood elves relish in the arcane.