Yogapedia explains Consciousness
Some yogic philosophers, such as Swami Kriyananda, believe that consciousness is the absolute or purest state. Matter is seen as the manifestation of vibrating energy; and that energy itself is seen as the manifestation of Consciousness. In this sense, it is said that consciousness cannot be defined because once it is, it is no longer pure.
Yogic practices, such as mindfulness and meditation, allow practitioners to explore and understand the nature of consciousness through introspection, or examination, of the mind. To better understand consciousness, the practitioner shifts their focus from the things they are aware of to the instrument of their awareness, which is Consciousness itself.
Many yogis believe that the state of individual consciousness is just part of a collective universal Consciousness, like a wave is part of an ocean. In this sense, Consciousness is what connects all beings and things.