This text is worth to give a view on mind:
There are many aspects to the mind, but two stand out. The first is the ordinary mind, called by the Tibetans sem. One master defines it: "That which possesses discriminating awareness, that which possesses a sense of duality – which grasps or rejects something external – that is mind. Fundamentally it is that which can associate with an 'other' – with any 'something,' that is perceived as different from the perceiver." Sem is the discursive, dualistic, thinking mind, which can only function in relation to a projected and falsely perceived external reference point.
So sem is the mind that thinks, plots, desires, manipulates, that flares up in anger, that creates and indulges in waves of negative emotion and thoughts, that has to go on and on asserting, validating, and confirming its "existence" by fragmenting, conceptualizing, and solidifying experience. The ordinary mind is the ceaselessly shifting and shiftless prey of external influences, habitual tendencies, and conditioning: The masters liken sem to a candle flame in an open doorway, vulnerable to all the winds of circumstance.
Seen from one angle, sem is flickering, unstable, grasping, and endlessly minding others' business; its energy consumed by projecting outwards. I think of it sometimes as a Mexican jumping bean, or as a monkey hopping restlessly from branch to branch on a tree. Yet seen in another way, the ordinary mind has a false, dull stability, a smug and self-protective inertia, a stone-like calm of ingrained habits. Sem is as cunning as a crooked politician, skeptical, distrustful, expert at trickery and guile, "ingenious," Jamyang Khyentse wrote, " in the games of deception." It is within the experience of this chaotic, confused, undisciplined, and repetitive sem, this ordinary mind, that, again and again, we undergo change and death.
Then there is the very nature of mind, its innermost essence, which is absolutely and always untouched by change or death. At present it is hidden within our own mind, our sem, enveloped and obscured by the mental scurry of our thoughts and emotions. Just as clouds can be shifted by a strong gust of wind to reveal the shining sun and wide-open sky, so, under certain special circumstances, some inspiration may uncover for us glimpses of this nature of mind. These glimpses have many depths and degrees, but each of them will bring some light of understanding, meaning, and freedom.
This is because the nature of mind is the very root itself of understanding. In Tibetan we call it Rigpa, a primordial, pure, pristine awareness that is at once intelligent, cognizant, radiant, and always awake. It could be said to be the knowledge of knowledge itself.
Do not make the mistake of imagining that the nature of mind is exclusive to our mind only. It is in fact the nature of everything. It can never be said too often that to realize the nature of mind is to realize the nature of all things.