A Wyvern is a Dragon with two legs and wings and often a stinging tail.
In Dungeons & Dragons a wyvern appears as one of the less powerful types of dragon and obeys the general traits, with poison on their stinging tail and coloring that is typically a redish brown, though other colors exist. While somewhat intelligent and capable of speech, they don't tend to use it, being ambush predators that are hostile by default to most things. Despite their aggression, they are often used as mounts in various settings.
In Eberron wyverns are found on both Argonnessen and Khorvaire. Various sources state they are used as mounts and that the Arcane Congress have breeding programs for them, and presumably House Vadalis does as well. They are featured in Breland's heraldry, but Thrane is the one stated to maintain wyvern units. Those of Argonnessen are subjugated by the true dragons of the land and serve as mounts for their human sized servants. Wild wyverns of Khorvaire are hostile to everything, even other wyverns outside of mating season. Presumably, like pigs, domesticated wyverns are less hostiles to everything than their wild counterparts.