We can say that the view in which one or more faces of the object are not perpendicular to the rest of the faces, but are inclined projections, are the auxiliary views.
¿What are auxiliary views?
Initially, we must know that the views of an object or body are orthogonal projections associated with it.
In this sense, auxiliary views are a type of view that are characterized by arising from a change in projection plane, they are usually used when highly complex parts or objects must be represented.
¡Hope this helped!