It's interesting that OD&D and 1e both assumed the reader knew what an elf was. Basic and 2e onwards actually explain them. I think that reflects the fact Gary was writing from the idea his book was going to a ) was going to be reached from another game book (0e assumed familiarity with chainmail , 1e assumed you had played Basic) and b) you were being in introduced to the gang by someone who did, and would explain it, and thus he's not going to waste time explaining things you learned in other books. Basic and 2e onwards is written with the intent that you don't know what they mean when you say "elf" in D&D terms and explain it.
Chainmail has this on elves:
ELVES (and Fairies): Armed with deadly bows and magical swords. Elves (and Fairies) are dangerous opponents considering their size and build. They can perform split-move and fire, even though they are footmen. When invisible Elves (and Fairies) cannot attack — or be attacked unless located by an enemy with the special ability to detect hidden or invisible troops — but they can become visible and attack during the same turn. Those Elves (and Fairies) armed with magical weapons add an extra die in normal combat, and against other fantastic creatures they will perform even better:
vs.:
Goblins - add 3 dice to Combat Tables
Ores - add 2 dice to Combat Tables
Hero-types - Fantasy Combat Table, score 9
Super Heroes - Fantasy Combat Table, score 11
Wizards - Fantasy Combat Table, score 10
Wraiths - Fantasy Combat Table, score 8
Wights - Fantasy Combat Table, score 6
Lycanthropes - Fantasy Combat Table, score 9
Ogres - Fantasy Combat Table, score 7
Giants - Fantasy Combat Table, score 10
(see rule for Magical Weapons)
Morale Rating — 6 Point Value — 4