The Nine Titans were nine Titan powers that had been passed down through the Eldian people for nearly 2,000 years after Ymir Fritz's death, each of them having their own name. They were called the Founding Titan, the Colossal Titan, the Female Titan, the Beast Titan, the Armored Titan, the Attack Titan, the Jaw Titan, the Cart Titan and the War Hammer Titan.
History: Around 2,000 years ago, Ymir Fritz obtained the Power of the Titans and became the first Titan, the Founding Titan. Thirteen years later, she died and her power was then divided between her three daughters who had been forced by their father to consume her remains. Eventually, the powers would split further into the individual Nine Titans, which were subsequently inherited by nine of her descendants.
Abilities: The Founding Titan had the ability to control Titans with its screams. Its screams could affect humans as well, altering their memories, but certain bloodlines were unaffected. Only Eldians containing royal blood were able to use its abilities; however, as shown when Eren screamed and punched Dina Fritz's Titan, a member of non-royal blood was capable of using the Founding Titan's ability via physical contact with a member of the royal family while in Titan form.
Trivia: Many transformed Titan forms are modeled after mixed martial artists. For instance, the Armored Titan is modeled after and Eren's Titan is modeled after . Grisha Jaeger consuming the Founding Titan and Eren Jaeger consuming the War Hammer Titan are the only known cases where a person inherits one of the Nine Titans while already having one.
Source: Nine Titans (Anime), available under CC BY-SA 3.0.