Aham, a concept of Kashmir Shaivism, is defined as the supreme heart (hṛdayam), transcendent Self, supreme I awareness  or infinite consciousness. The space of Aham is where khecarī mudrā (free movement in the space of the heart) is realised. Khecarī mudrā is considered the supreme state of spiritual evolution.
When Śiva wants to create, the first step is said to be the creation of an interior space (the space of his heart) - a matrix of energies that will be the substrate of the new world. This place is called Aham which means "I" in Sanskrit. Thus the absolute first creates the divine person, Aham, and from this divine person will appear the manifestation itself.
Aham is identical to mātṛkā (the wheel of phonematic energies), essential nature of all categories from Pṛithvī tattva (earth) to Sadāśiva tattva,. Aham is the final resting place, dwelling place, abode of all beings, receptacle of the world.
Another definition of Aham is that of primordial mantra, transcendental mantra, the so-called heart-bīja (mantra of the heart) - force and power of consciousness. As the supreme mantra, Aham is closely related to matravīrya (the potency of mantra). Thus the realization of Aham confers power over any mantra.
In Aham, the supreme (para) aspect of Śakti is realized. Aham is the Śakti of Śiva or in other words, the expansion of Śiva. Another way of describing Aham is as the union of Śiva and Śakti, the emittive (visarga) aspect of the Supreme (anuttara).
Aham is formed of A+HA+M, a triad of Śhiva (A), Śakti (HA) and bindu (M). M is the final point, union of Śiva and Śakti, where they dissolve into Paramaśiva. The triangle of A+HA+M is the essence of the Trika system. A+HA+M form the sṛṣṭi bīja (seed of emission), a mantra that is identical to the energy of expansion and creation.
Aham can also be defined as: A = abedha (non-differentiation), HA = bheda (differentiation) and M = bhedābheda (differentiation cum non-differentiation).
On the other hand, MAHA, mirror image of AHAM, is formed of MA+HA+A, and represents the saṃhara bīja (seed of reabsorption) - the mantra that is identical to the process of spiritual evolution, or in other words reabsorption of the manifestation back into the absolute. In MAHA, Śakti (HA) enters bindu (M) (the limited being) and reunites it with the Supreme (A).