The Will to Power, as Nietzsche would put it, is the underlying, foremost, dominant will.The basic premiss is that the Will to Power is the drive to make oneself powerful and to exert one's power on one's world. All other wills are derivative of the Will to Power. For example, one Wills to Live so that one may increase and exert one's power further. One Wills to Eat as nutrition increases strength/power and also because one requires it to survive, which leads to the Will to Live which leads to the Will to Power. One Wills to Procreate so that one's child may carry on one's legacy, memory and power. One Wills to Fame so that one's power influences as many persons as possible and that so one has as power over as many people as possible. One Wills to Knowledge as knowledge can be used to become powerful. One Wills to Relationships so that one may have power over these relations.

As the Will to Power is the primary will all actions willed that decrease power are caused by a self-destructive, self-opposing will. For example, the Will to Suicide comes when one's will has been inverted in such a way; suicide leads to a loss of power (most of the time; one might garner post-humous fame if one does commit suicide, an action under those intentions is an example of the Will to Power.)

Nietzsche would argue that the Will to Power is innate in human biology, that it is a primal urge. A child is an apparent example of the Will to Power; the child kicks and screams at the world and it's mother to exert it's power on them, It will eat and sleep when ever it has the oppurtunity to do so so that it may grow and become more powerful. Only when the child grows older and learns that it must contain and control itself more in order to advance socially and therefore become more powerful does it stop exerting it's will upon the world in the most immediate way.

Practically, this would mean that the healthiest and strongest will would be the one which freely exhibits the Will to Power in all instances and never opposes it. For example, a healthy will shall not wish to give money to charity as there is only a loss of power in such an instance. There might be cases, however, that when you donate a huge sum of money to charity that you then receive attention from the community and thus become more popular and therefore more powerful. If one is to have a healthy and strong will then it follows that one should always maintain this power orientated mindset. This is extremely contradictory to contemporary moralities held commonly today such as utilitarianism and egalitarian morals. This is part of the basis upon which Nietzsche attacked Christianity as the religion is directly opposed to the Will to Power and therefore directly opposed to man's innate nature and desires.

Nietzsche was a strong humanist. He wanted to find out as much about man's nature as possible and encourage one to embrace that nature. As such he was a psychologist himself and encouraged all forms of science as they all lead to knowledge which helps us to gain understanding of man's nature: man's physiology and man's Universe (the Universe in which man belongs to, not the other way around.)

The Will to Power drives one to exert one's power such as the child does. However, one chooses to conserve themselves and not act in this child-like way so that they may, in the grander scheme, gain more power so that they can exert as much power as possible onto the world. It is comparable to immediate pleasure / long-term pleasure. As such, the Will to Become More Powerful is the derivative of the Will to Exert Power and these two wills are collectively called the Will to Power. For example, one chooses to write a book so that one's power may be continually exerted through their writings when another is influenced by them. However, this is my interpretation and not necessarily Nietzsche's exact thoughts. Perhaps I am confusing the matter, perhaps the Will to Exert Power and the Will to Become More Powerful are completely inseperable.