...five skandhas are..
The Sanskrit word skandha literally means a group, a heap, or an aggregate. In Buddhist tradition, the five skandhas of form, feelings, perceptions, impulses and consciousness are taken to constitute the entirety of what is generally known as "personality." These four words ("five skandhas are empty") are the essence of the earliest Buddhist teachings. The Buddha taught the three marks of existence (suffering, non-self and impermanence) as the defining characteristics of individual human existence; to these three marks, the Mahayanists added the fourth mark of sunyata (emptiness) and extended the concept to each and any existent in the universe. A detailed look at the five skandhas will mean understanding the very basis of Buddhist teachings and will provide a solid foundation for an extended look into sunyata.
The first and the most obvious of the skandhas is the corporeal form (Sanskrit: nama-rupa) which comes into being as a result of the energies of four elements (earth, air, fire and water) coming together in a certain configuration; when looked at by quantum physics, a form is seen to be devoid of any solid, everlasting substance. The form is held together in time and space by the interacting energies of the four elements in a certain pattern and balance. The characteristics which all skandhas, whether physical or mental, share are: arising, stabilizing, decay and dissolution. Decay and dissolution occur when the balance in which the elements have been held together for a certain period of time loses its inner tension and the organism is left without the essential vitality to hold itself in time and space.
The skandha called feeling (Sanskrit: vedana) is the general concept for feelings and sensations. These feelings and sensations can be classified into pleasant, unpleasant and neutral. As with the skandha of corporeal form, feelings and sensations also arise as a result of certain factors coming together. They then gain an intensity, hold it for some time, lose the intensity after some more time, and finally disappear. A particular feeling or sensation may change into another feeling or sensation which, in turn, will go through the same process ad infinitum.
The skandha called perception (Sanskrit: samjna) includes perception of form, sound, smell, taste, touch and bodily impressions, and mental objects. Perception takes place only in relation to an object (or thought) and does not exist independently of an object of attention.
The skandha called impulse (Sanskrit: samskara) refers to mental formations. In Abhidharma-pitaka, the traditional compend-ium of Buddhist psychology, a total of fifty-two impulses are listed, and include mental activities such as volition, attention, discrimination, joy, happiness, equanimity, resolve, effort, compulsion, concentration, and so on; included in this skandha are all the volitional impulses or intentions that precede an action. Since actions can be either physical, verbal, or mental, impulses can accordingly be physical, verbal or mental. This skandha refers both to the activity of forming and the passive state of being formed. The impulses thus are the impressions, tendencies, and possibilities in one's consciousness, and are the sum total of one's character. The impulses are the result of the totality of one's actions and thoughts, including those of earlier births, and their continuing presence is the condition for a rebirth. If they are absent, no karma is produced and no further birth takes place. Since the impulses can be good, bad or neutral, they determine the type of rebirth that will take place since their quality conditions consciousness, and through them consciousness seeks a form in rebirth to manifest those qualities.
The skandha called consciousness (Sanskrit: vijnana) is the faculty of knowing. Consciousness is a reaction or response which has one of the six organs (of eyes, ears, nose, tongue, body and mind) as its basis and one of the six corresponding external phenomena (visual form, sound, smell, taste, touch and mental thoughts) as its object. Consciousness arises out of contact between the object and the corresponding organ, but consciousness does not recognize an object itself. It is only a sort of awareness, awareness of the presence of an object. For instance, when eye comes into contact with a blue color, eye-consciousness simply "sees" the presence of a color. The recognition that the color is blue comes from the skandha of perception, the third aggregate discussed above. Likewise, the hearing-consciousness only hears the sound but does not recognize the category of sound; this is done by the perception-aggregate, and so on.
A commonly-made mistake about consciousness is to misunderstand it as some sort of soul or permanent self or continuum that proceeds through one life and onto the next. The Buddha taught that consciousness arises only out of conditions; without the presence of conditions there is no consciousness. Consciousness depends on form, feelings, perceptions and impulses for its arising and cannot exist independently of them. It is essentially an observing function.