In many fantasy settings, Elves come in a large number of varieties (a tendency often lampooned as "an elf for every occasion"). One of the more common varieties are High Elves, which are usually the setting's "default" elven race. In most(but by no means all) cases, they will be pretentious assholes who rest on the laurels of their civilization that was probably once the greatest in the world, ignoring the fact that the round-ears are catching up or have exceeded them.
Lord of the Rings
The central elves of the book series are known as the High Elves and also the Eldar, hence where Games Workshop got their own names for their own elves in fantasy and elves in space respectively. They are responsible for impacting on the personification of High Elves in many fantasy settings afterwards. In the context of the series, the label "High Elves" is primarily used to describe the Noldor, one of the three ethnic groups of elves and the most advanced in terms of craftsmanship. They are "high" in comparison to the other elves of Middle Earth, with the Sindar elves having their own robust civilization but not quite as advanced as the Noldor, and the Silvan elves, who basically are the archetype for Wood Elves. They're effectively immortal (in that they are ageless and can't die from disease or old age), unearthly beautiful and a wicked shot with a bow and a deadly strike with a sword. At first the Noldor had intentions of being the dominant power in Middle-Earth, but after their ass-whooping at the hands of Morgoth, they've been gradually migrating back to the Undying Lands, with increasingly less contact with the other nations of Middle-Earth, to the point that their large kingdoms have disappeared into tiny, hard to enter enclaves.
Dungeons & Dragons
High Elves have been the "face" of elfdom throughout the history of Dungeons & Dragons, representing the more civilized, Tolkien-inspired citybuilding [[wizard]ry-practitioners in contrast to the nomadic hunter-gatherer Wood Elves. As a result, the high elves tend to have the most cultural splits/ethnicities/whatever you wanna call 'em in D&D, especially in settings made by TSR.
An early concept of D&D that slipped into obscurity, Gray Elves occupy a nebulous position between being a distinct High Elf culture and an actual biological subrace, with distinct statblocks in both AD&D and 3rd edition. They are generally described as "High Elves turned up to 11", being incredibly powerful mages even by elf standards... and also being elitist douchebags even by elf standards.
In the World Axis, High Elves technically don't exist. See, when they were designing Dungeons & Dragons 4th Edition, the decision was made to emphasize the split between High and Wood Elves to a greater extent than ever before, and the High Elves were redesigned as almost an entirely separate race, now being named the Eladrin, whilst Wood Elves were simply known as "elves".
That said, the high elf archetype didn't entirely disappear. After the Player's Handbook 3 set a new rule that PC races received a +2 to two of three possible ability scores at character creation, elves gained the ability to swap their +2 Wisdom bonus for a +2 Intelligence bonus, which in turn made them better suited for Arcane classes and thus allowed them to represent High Elves as they were in older editions. Some Forgotten Realms material released after this point also offered the option of tweaking the skills and proficiencies of the eladrin for an alternative take on the high elf.
In a nutshell, not only did this give players more versatility in how they designed their elf character, it also gave dungeon masters greater flexibility in defining their world's particular take on elves! The forgotten "Dusk Elves" by their own lore worked significantly better by using the "Elf with +2 Int" as their mandatory stat bonus, whilst the ability to give Eladrin the Elf Weapon Proficiency trait instead of their own Eladrin Weapon Proficiency trait could further customize eladrin cultures - and the Sun Elf's handling as an Eladrin with free proficiency in Wizard implements could even be used to revive the Gray Elf concept.
The former High Elves of the Scarred Lands, now known as the Forsaken Elves, are a doomed race (like the name suggests). In the not!Titanomachy they managed, at the cost of their patron god Jandaveos and most of the young, to slay a Titan: Chern. Something a mortal race should not be able to do. With his death throes, Chern cursed the remaining High Elves with a divine malady; the inability to bear pure-blooded children, thus dooming the race to extinction.
Too stubborn and prideful, they refuse to embrace a new divine patron to potentially lift this divine curse. Instead, they've resorted to kidnapping young Human children to raise as breeding stock, or buying Human slaves to breed Half-Elves. And it works, their progeny are healthy, strong and full of life. But then they treat their halfbreed progeny like absolute shit for being half-human, and are then surprised when they tend to run away in huge numbers to Ghelspad, where they are treated decently.
The Warcraft high elves were wood elves that became addicted to arcane magic. This has not gone especially well for them, but has not altered their Elven arrogance in any way. In the Warcraft supplements for D&D, they were a level adjustment +1 race. They gained the equivalent of Sudden Empower, gain +1 spell/day, and no penalties to spellcasting for their level adjustment, but took twice as long to prepare spells and had trouble taking levels in non-spellcasting classes once they started.
See High Elves (Warhammer) for further details.
These elves took the idea of a dying race from Tolkien and took it a step further, adding the grimdark of the setting to concept. Now the Warhammer High Elves have no safe place to retreat to, their birth rate is declining and their people dying and their culture is under constant threat of destruction. So yes pretty grimdark indeed. But unlike Tolkien's elves, they're not at all passive about it, and this raw stoicism in the face of what seems to be inevitable destruction makes them Awesome.