I cannot put the description better than that of Bhikkhu Bodhi. This article that follows was found at http://beyondthenet.net and is believed to be in the public domain. I have restructured it into one contiguous page rather than it’s original format but I believe it to be one of the best and briefest explanations of the five aggregates that I have found.

This is such an important subject for people to get their head around so I have placed it on the right hand menu as a separate subject. The post may need reading several times to grasp it, at least I had to do so, I intend no slight on the reader if they get it first time through.

The Five Aggregates Of Clinging – By Bhikkhu Bodhi

The Buddha reveals that what we are, our being or personality, is a composite of five factors which are called the five aggregates of clinging. They are called the five aggregates of clinging because they form the basis for clinging. Whatever we cling to can be found amongst the five aggregates. These five function together as the instrument for our experience of the world. We cling to them as instruments of our experience in this life, and when they break up at death, due to that same clinging – the desire for enjoyment and for existence – a new set of aggregates, a new life arises to continue our experience in another existence. Thus we build up one set of aggregates after another, life after life, and in that way we accumulate Dukkha, the suffering, in the round of samsara. The Buddha says that the five aggregates have to be fully understood. This is the first Noble Truth, the truth of Dukkha. The five aggregates are our burden, but at the same time they provide us with the indispensable soil of wisdom. To bring suffering to an end we have to turn our attention around and see into the nature of the aggregates.

The Five Aggregates are:

I. MATERIAL FORM
This includes all the material factors of existence, every type of material phenomena. The most important of these is the body, the physical organism through which one experiences the world. The Buddha analyses the aggregate of material form into two basic substances:

1) The Four Primary Elements
For Buddhists these do not mean literally the natural earth, water, fire and air. Rather, they symbolise four behavioural properties of matter common to all material phenomena, the properties that every material body exhibits.

1. Earth element This is the property by which a material body has some degree of hardness or softness, roughness or smoothness.
2. Water element This represents the property of cohesion. Because of the water element, material particles bind together and adhere to one another.
3. Heat element This is the principle of heat by which all material phenomena possess some degree of heat. Even when a particular substance feels cold to us, that is only becasue it contains less heat than our body. But every material body possesses some degree of heat.
4. Air Element This is the principle of distention, by reason of which all material particles are in a state of vibration. By reason of the air element, material bodies exhibit a motion.

Now all material phenomena possess these four elements to some degree. What distinguishes them is the proportion in which the primary elements are combined. We discriminate the types of matter on the basis of the dominant element. Thus we find solid bodies, liquids, gases and forms of energy depending on the proportions or predominance of the four primary elements. But all four elements are present to some degree in every unit of matter.

2) The Secondary Elements of Matter
Besides the primary elements, there are a number of secondary types of matter, material forms derived from the primaries. They are :

1. Five sensory receptors.  These are the sensitive tissues of the sense faculties, eye, ear, nose, tongue and body. The sensitive matter by reason of which eye can receive sight, nose can receive smell, ear can receive sound, tongue can receive taste and body can receive touch sensation.
2. The first four sense data. Colour, sound, smells and taste are also secondary types of matter. The touch sensation however, is provided by the primary elements themselves.
3. Life faculty The faculty which vitalizes the body and keeps it alive.
4. Mental base Organs and nerve tissues which function as support for consciousness in the thought process.

The aggregate of form comprises the entire material side of existence. The mental side is distributed amongst the other 4 aggregates.

The mind for Buddhists is not a simple unit, but a complex cooperative activity involving four Factors: feeling, perceptions, mental formations and consciousness.

II. FEELING
Feeling is the mental factor that has the function of experiencing the ‘flavour’ of the object, the effective quality of the object. There are three basic types of feelings – pleasant, painful and neutral feeling. Feeling can further be subdivided by way of the sense faculty through which it originates: feeling which arises by contact with the eye, ear, nose, tongue , body and mind, which amounts to eighteen types of feeling (three kinds each through six sense faculties).

III. PERCEPTION
This is the mental act of grasping the distinguishing qualities of the object. Perception takes note of the object’s features, it identifies and notes.

Perception is divided into six categories by way of the sense objects that it takes note of:

1. Perception of form
2. Perception of sound
3. Perception of smell
4. Perception of taste
5. Perception of touch
6. Perception of ideas

IV. MENTAL FORMATIONS
This is a comprehensive group which contains a number of volitional factors. In Abidhamma 50 types of mental formations are mentioned. Of these, the most important is volition or will. This is the mental factor which arouses us to act by way of body or speech. Mental formations also include all different desires and emotions, including the wholesome and unwholesome roots. These are the basic psychological roots of unwholesome actions: greed hatred and delusion, and the basic roots of wholesome actions: generosity, loving kindness and wisdom.

V. CONSCIOUSNESS
Consciousness is the key factor of the mind. It is the basic awareness of the object, the light of awareness which makes all experience possible.

Consciousness is divided into six types by way of its bases:

1. eye consciousness – cognizes visual objects.
2. ear consciousness – cognizes sound
3. nose consciousness – cognizes smell
4. tongue consciousness – cognizes taste
5. body consciousness – cognizes tangible sensations
6. mind consciousness – cognizes objects of outer senses such as sights, sounds… etc. as well as mental objects such as ideas, concepts, images, abstract notions etc.

Consciousness seems similar to perception, but these two perform different functions. Consciousness is the general awareness of objects, while perception is the specific factor which grasps the object’s distinctive qualities.

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These five aggregates exhaust our psychophysical existence. Any event, any occurrence, any element in the mind-body process can be put into one of these five aggregates. There is nothing in this whole experiential process that lies outside them.

All these four mental aggregates always exist together; they all depend upon one another. Whenever there is any experience of an object, at that moment there is present, simultaneously, a feeling, a perception, a cluster of mental formations and consciousness, the light of awareness.

Whatever we identify ourselves with, whatever we take to be ‘I’, or ‘my self’ can be found within these five aggregates. Therefore if we care to understand ourselves, what we have to understand is the five aggregates. To fully understand the five aggregates means to see them as they really are, and this means to see them in terms of the three characteristics of existence, that is, impermanence, unsatisfactoriness or suffering, and selflessness or non-self.

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Original text found at http://beyondthenet.net/dhamma/fiveAggregates.htm and is believed to be in the public domain. Please use the contact form available should this not be the case.