Religion is a belief system that consists of a set of common myths, rites, practices, sacred texts, and ethics that tends to organize large human groups based on the belief of a transcendental or spiritual order to which that particular group, or the entire humanity, is linked.
In this sense, religion works as an ideology through which large groups of people who do not know each other can cooperate together towards one particular goal. Throughout history, religion worked as an amalgam for large groups to set a common ground of understanding, belief, and moral. It made possible, for example, for ancient Egyptians to build the pyramids, and in general, it provided a supernatural justification for the political order, and it prompted the emergence of big empires that extended in space and time.
However, since there were many religions throughout the world and throughout history, and since most of the great religions have a universal vocation, they tended to collide between them in order to impose their particular worldview. In this sense, religion creates more space between people and, often, they give reasons for religious wars.