Short answers, pulled from the story.
The half-elf first appeared as a player character race in the Greyhawk supplement to the original 1974 edition of Dungeons and Dragons. The Monster Manual published in 1977 included the half-elf alongside other creatures.
Half-elves live about 180 years according to game lore descriptions. They possess long ears similar to elves yet maintain skin paler than human standards.
Tanis Half-Elven serves as the main character of the initial Dragonlance series. His name implies his heritage directly within that narrative world.
The total count reached 10,454 characters out of every 100,000 created during this period. Wizards of the Coast reported these figures showing half-elves ranked third among all races.
August 2022 saw Wizards of the Coast launch the One D&D public playtest which removed distinct rules for half-elves. Lead designer Jeremy Crawford commented that they are not comfortable with options starting with half due to inherent racism.