Decision-making is often regarded as the mental process, or a cognitive process, that results in the selection of one course of action. The selection would have been chosen instead of one, or many other, alternative scenarios. Every decision making process will ultimately produce one final choice, and this is one of the many intellectual processes that we go through every day. The end product of the decision making process could either be an action, or even an opinion of choice.
The human performance, in terms of decisions, has for years been subject to extensive research from a number of different perspectives. From the psychological perspective, it's completely necessary for individual decisions in the context of one set of needs, to be examined. The preferences that an individual may need or seek must be examined as well.
From the cognitive perspective, the process needs to be regarded as a continuous process that is integrated in the interaction with the environment.
However, from a normative perspective, analyzing an individual decision is very much associated with the logic of decision making, as well as the rationality and invariant choice that it can lead to.
However, at another level, decision making may even be regarded as problem solving, which is ultimately terminated when a satisfactory solution has finally been reached. Hence, decision making is both a reasoning and emotional process that can be either rational or irrational, and can be based on either tacit assumptions or explicit assumptions.
For more information on thought process, intellectual processes and decision-making, there are many articles about them to be found at www.wikipedia.org. Simply type in the process you want to read about and there will be a lengthy article.