The ultimate motivation behind segmentation is the recognition that people are different and have different beliefs and needs and therefore make choices based on different criteria. The basic principle of segmentation is to divide the universe (consumers, brands, organisations etc.) into discrete groups according common criteria, such as their attitudes, needs or beliefs; each of these groups can then be addressed separately and the brand, service or product offered to them tailored accordingly.
The result is discrete groups whose members are as similar as possible to each other in terms of needs or motives and who are as different as possible from other groups. The most basic segmentations, such as demographic or behavioural make the assumption that individuals with similar characteristics can be treated in the same way.
These basic segmentations go some way to maximising return on marketing/selling activity, but it is easy to see that more sophisticated segmentations such as behavioural, needs based, category based or loyalty segmentations, can help get even better returns on investment.