The Chittamatra (Tib. semtsampa; sems tsam pa) or 'Mind Only' School is a Mahayana school. They say that all phenomena are merely mind--the all-ground consciousness manifesting as environment, objects and the physical body, as a result of habitual tendencies stored within the all-ground.
The Three Natures
They divide all phenomena into the ‘three natures’: the imputed or 'imaginary, the dependent, and the truly established.
The Chittamatra View of the Two Truths
Khenpo Ngakchung says:
All the dualistic phenomena of the imputed nature and the mind and mental phenomena of the dependent nature are the deceiving phenomena of delusion, the relative truth. The essence of the dependent nature, which is the naturally luminous consciousness, and the fully established nature, which is the fact that this [i.e., the dependent nature] is empty of the dualistic projections of the imputed nature—comprising the nature of reality and wisdom—are said to be the absolute truth.