Alaric is a human, vampire hunter, former history teacher at Mystic Falls High School and a former Enhanced Original, not by being one of the first vampires as the Mikaelson Family is, but instead being turned through an altered version of the spell used on the Mikaelson family.

How is Alaric like an original?

Alaric became an Enhanced Original Vampire through Esther's magic so he could kill her children with the last, and indestructible, White Oak Stake, to make the vampire species extinct before his death, his life having been linked to Elena's. This lead Rebekah to kill her to stop Alaric.

Is Alaric still an original vampire in legacies?

During the sixth season, Alaric is resurrected as an Enhanced Original Vampire and is forced to live without Damon for some time. Alaric even assists Elena and compels her to forget about Damon because she grieves his death too much.