Elves and Half-Elves have Fey Ancestry, which states
You have advantage on saving throws against being charmed.
What spells and effects are covered by this? Only Charm Person? Enchantment spells with a Wis save?
A good answer should contain either rule text and/or statements (tweets) by the 5e design team.
Charmed is a specific game condition. From Appendix A of the PHB (page 290):
Charmed
A charmed creature can’t attack the charmer or target the charmer with harmful abilities or magical effects.
The charmer has advantage on any ability check to interact socially with the creature.
So Fey Ancestry gives advantage on any saving throw to avoid receiving the Charmed condition. Or to put it differently, a creature with Fey Ancestry has advantage on any saving throw made to avoid the effect of a spell, trap, or other effect that inflicts the Charmed condition.