It is a branch of philosophy which deals with questions regarding reality and existence

Philosophy is divided in many branches, this helps people to understand better all the types of  thinking. Each branch studies different subjects. 
This video will help you understand how Philosophy is divided.

Taken from: http://www.youtube.com/watch?v=fzyteeh6-cs

"MetaphysicsWhat is Metaphysics?Metaphysics is the branch of philosophy responsible for the study of existence. It is the foundation of a worldview. It answers the question "What is?" It encompasses everything that exists, as well as the nature of existence itself. It says whether the world is real, or merely an illusion. It is a fundamental view of the world around us.

Why is Metaphysics important?Metaphysics is the foundation of philosophy. Without an explanation or an interpretation of the world around us, we would be helpless to deal with reality. We could not feed ourselves, or act to preserve our lives. The degree to which our metaphysical worldview is correct is the degree to which we are able to comprehend the world, and act accordingly. Without this firm foundation, all knowledge becomes suspect. Any flaw in our view of reality will make it more difficult to live.

"Ethics: the study of values in human behavior or the study of moral problems: e.g., (1) the rightness and wrongness of actions, (2) the kinds of things which are good or desirable, and (3) whether actions are blameworthy or praiseworthy.

1. "We may imagine a squad of soldiers to be practicing the throwing of live hand grenades; a grenade slips from the hand of one of them and rolls on the ground near the squad; one of them sacrifices his life by throwing himself on the grenade and protecting his comrades with his own body. It is quite unreasonable to suppose that such a man must be impelled by the sort of emotion that he might be impelled by if his best friend were in the squad."
2. Did the soldier who threw himself on the grenade do the right thing? If he did not cover the grenade, several soldiers might be injured or be killed. His action probably saved lives; certainly an action which saves lives is a morally correct action. One might even be inclined to conclude that saving lives is a duty. But if this were so, wouldn't each of the soldiers have the moral obligation or duty to save his comrades? Would we thereby expect each of the soldiers to vie for the opportunity to cover the grenade?"

This is an example of some questions you can find in this page.
If you want more examples of every branch, you can visit this page: http://philosophy.lander.edu/intro/what.shtml

"Epistemology is that part of philosophy that asks "what can we know?" "What can we be sure of?" "How do we get beyond mere opinion to real knowledge?"

Traditionally, there are two approaches to epistemology:

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