In Buddhism, one of the Five Aggregates. To review, the five are:
In particular, conception refers to the faculties of the mind responsible for grouping and ordering external stimuli into concepts. That is, the faculty of conception organizes the raw data gathered by through the senses (see sensation, another of the Five Aggregates) into recognizable intellectual categories. Through the faculty of conception, the mind organizes and groups sensory data, and fits it to one or more categories. This grouping of shapes, colors, and smells is a 'horse'. These sensations are 'pain'. At this level, the mind makes no value-judgement about good and bad (that's the role of discrimination), it merely overlays conceptual labels on raw sensory data.
This process can be very illustrative of the Buddhist idea of no-self, known in Sanskrit as anatman and in Pali as anatta. When the faculties of conception place a particular mental label over a group of phenomena (or, to use the jargon, a group of dhammas), there is no hidden 'essence of blank' that identifies the object of perception as one thing and not another. The word 'table' is simply a conceptual label applied to a grouping of structures that we percieve with the faculties of sight, touch, and, if we spill something particularly tasty on it, taste. If you cut up the table, it does not cease to be a table because some hidden 'essence of table' has fled to the four winds. Rather, it is because the table no longer resembles what we have defined a table to be.
In the same way, Buddhism teaches that what we term a human being is nothing other than the Five Aggregates. When the Five are present, we apply to them collectively the label of human being. There is no 'essence of human' that appears when the Five are conjoined, it is merley that when all five are present, it fits what we call human. Thus it is said that there is no-self or no-soul, because there can be found no permanent, immaterial essence that makes humans human, at least nothing that corresponds to the Hindu and Vedic notion of the soul or atman. Thus, conception treats the human being the same as all other sense objects, physical and mental (there are six senses in Buddhism, not because of abiding faith in ESP, but because thought is regarded as a sensory object).
This, ultimately, seems to me to be what is meant by the teaching of anatta. That human beings are the same sort of entity as everything else in the world- a compound of non-human components. While human birth may be a privileged category because of the opportunities it provides, it would be an error to regard a human of being possessed of some unknown quantity that constitutes hidden essence of humanity. We are, in the end, really no more than the sum of our parts. They may be some rather nifty parts (particularly in the mental realm), but the same truth still holds.
Of course, there is much more complexity than this to the concept of conception, as well as the teachings of anatta/anatman. In the tradition of the Abhidhamma, one would break down and list the possible types of conceptions, those dhamma that interact with conception, and the dhamma that result. For further reference, visit your local learned Theravada bhikkhu, or take a peek at the Abhidhamma, either in the form of the Abhidhamma Pitaka, or through some of the more popular manuals and guides to the same that are now available in the West. See also the nodes relating to anatman, anatta, atman, and the rest of the Five Aggregates.