That’s a great question! Spoilerons are simply spoilers that work like ailerons. A spoiler raises on the down-going wing and spoils airflow, reducing lift. That wing then drops, allowing the airplane to roll. Although spoilerons can replace ailerons, they usually work in tandem with ailerons and are typically found on fast jets. Typically, both devices are operated at low speeds, while only one surface is used at higher speeds.
You can read more about spoilerons at Wikipedia.