Kashmir Shaivism is more accurately known as Trika Shaivism and refers
to a nondualist tradition of Saiva-Sakta Tantra which originated sometime after 850 CE. Though this tradition was very influential in Kashmir and is thus often called Kashmir Shaivism, it was actually a pan-Indian movement termed "Trika" by its great exegete Abhinavagupta, which also flourished in Odisa and Maharastra. Defining features of the Trika tradition is its idealistic and monistic Pratyabhijnā ("Recognition") philosophical system, propounded by Utpaladeva (c. 925–975 CE) and Abhinavagupta (c. 975–1025 CE), and the centrality of the three goddesses Para, Parapara, and Apara.
they were the first attempt
to present a non-dualistic metaphysics and gnostic soteriology in opposition to the dualistic exegesis of the Shaiva Siddhanta.
Kashmir Shaivism and Advaita Vedanta are both non-dual philosophies that give primacy to Universal Consciousness (Chit or Brahman), in Kashmir Shaivism, all things are a manifestation of this Consciousness, but the phenomenal world (Sakti) is real, existing and having its being in Consciousness (Chit).