Officially, Ilocano refers to the people and Iloco refers to the language but, in reality, people just use Ilocano to refer to both.

Used as the lingua franca of Northern Luzon, Ilocano is also spoken in Pangasinan, Nueva Ecija and Vizcaya, and, for the old generation, Aurora Province. The language is not limited to these areas though since you can find Ilocano speakers in Vizayas, Mindanao, and even Hawaii (and other parts of the US) where a lot of Ilocanos migrated in the 90s.