It is hard to truly define religion in one way because religion encompasses so many different things depending on which religion is being referred to. There are literally thousands of religions that exist in the world, and although people may follow them for similar reasons, they each create different human experiences depending on the type of religion.
Many religions are associated with the natural world and the power derived from the natural world. The natural world and it's forces are beyond human control, which is relevant to the fear sometimes associated with religion. Religion also marks the encounter between supernatural beings such as God/gods, spirits, demons,etc and humans. Religion is also associated with "the ultimate concern." The ultimate concern is commonly discussed in regard to understanding the after-life. The ultimate concern is also one of the reasons that some people choose to "believe" or choose to be religious because they are concerned about what will happen as a consequence if they are not. Religion is also a human response to sacredness and divinity. Sacred scriptures, relics, and practices help those who believe in them understand human origin and our purpose in this world.
Although all of these things can be used to describe what religion is and how it functions, religious practice is a highly individual experience in regard to how deep into it one may be, and how being religious will impact that person.
84% of the World's population identifies as being religiously affiliated. Christianity is the leading religion in the world with 35% of those who identify as being religiously affiliated, claiming Christianity. The second largest religion in the world is Islam, encompassing 23% of the World's population. Adherents to Hinduism make up 15% of the World's population, which is interesting because 94% of these people inhabit the Indian sub-continent. Adherent to Buddhism make up about 7% of the World's population. 6% of the World's population follows folk religions, usually found in Africa or among Indigenous peoples. 1% of the World's population follow religions commonly classified as "other," such as: taoism, sikhism, wicca, etc. And Judaism has 0.2% of the World's population as adherents.
All of the people described above, 5.8 billion people, openly identify with religious culture. Many of which are born into it, or brought into it as a child, but choose to continue their faith into adulthood. Is there a reason for this? Does religion help us prosper?