All religions essentially try to answer the big questions about life. How does one go bout living a meaningful life? What is the nature of the universe? Is there life after death? Is there a spirit world? Religions present their own answers to these questions, usually in the form of creeds, which their followers are expected to accept.
Religions also answer questions regarding morality and proper behavior. People turn to religion when wondering how they should conduct themselves in regards to other people. Many religions have some form of what is commonly called the golden rule, that is, the idea that people should treat one another as they wish to be treated. However, religions often vary on specific cultural questions, such as how to approach sexuality, marriage, eating, and so forth.
Religions often use rituals during worship. Rituals are a ceremonial set of gestures and phrases meant to be executed in a particular order. They can be reenactments of a religion's particular set of myths, ways of giving thanks to the religion's god or gods, or rites of passage. Examples of religious rituals include the communion supper for Christians, puja for Hindus, Hajj for Muslims, and the Passover Seder for Jews. Many religions also have chanting practices.
Community is another major part of most religions. Believers gather in houses of worship in order to pray together or conduct public worship. They also observe religious festivals together.
The four major world religions, measured by the number of adherents, are Christianity, Islam, Hinduism, and Buddhism. Other religions with substantial numbers of believers include Judaism, Sikhism, and Jainism. Some points these religions have in common include the following:
1. Religions have a creed, a statement of belief which makes it possible to convert to the religion. Christianity and Islam, which actively seek converts, have the simplest creeds. Muslims, for instance, believe that "there is no God but God, and Muhammad is his prophet." Although religions which do not proselytize tend to have more complex sets of beliefs, there is still a collection of propositions about the world, the acceptance of which makes you a Buddhist or a Hindu.
2. Religions form communities that gather together in specific buildings designed for the purpose of worship. Churches, mosques, and temples all tend to be striking constructions which are clearly central to the communities in which they are built.
3. There is generally a specific ritual of form of worship which is followed when adherents meet, though in some sects, this may be very informal.
4. Religions perform several functions, one of the most important of which is to answer questions. These include questions about the nature of the world (How did the universe come into being? What will happen to me after I die?) as well as moral questions (In such a situation, what ought I to do, and why?).
Something that the five major world religions (Christianity, Judaism, Buddhism, Hinduism and Islam) have in common is a sense of community. A sense of community provides group cohesion and identity, as well as a way for rituals and traditions to be passed down from generation to generation. For Christians, this community most often centers around a church. For members of the Jewish faith, the synagogue and yeshiva (Jewish school for the study of the Talmud and Torah) serve as focal points for the community. The sangha, which refers to a monastic community of monks or nuns and the lay community that supports them, is the central cohesive force in Buddhism. For Hindus, communities can form among devotees of a specific guru or deity, or among those who attend a specific shrine or temple. In Islam, a community can form within a local mosque or among followers of a particular imam. In addition, all Muslims consider themselves to be part of the worldwide community of Islam which is referred to as the ummah.
The practice of a religion is clearly one way of directing one's life with its structure and theological or other principles which govern behavior. Usually, there is a being superior to mere humans that religions recognize. However, there is a sharp division in beliefs among some religions that politicians and others would make murky.
Thomas Hobbes once commented that people explain that which they cannot explain in terms of "God." Most world religions deal with how its practicioners understand the world around them, how they got here, and where they are going. There is strong evidence that Neanderthals buried their dead with ceremony, thus indicating some belief in life after death. All world religions understand some sort of force or deity that influences life. It may not be well denominated as in the case of Buddhism; yet there is always the belief that there is some being which created the world and life and influences it to some extent. If this were not so, there would be no need for religion.
I would argue that the main thing that most religions have in common is a set of ethical beliefs. I am not saying that all religions share the same set of ethics, but I am saying that most religions have some set of ethics and that they believe those ethics are mandated by some supernatural forces.
In the Judaeo-Christian tradition, for example, there are the 10 Commandments. These were handed down by God to govern the ways in which people behave. But other religions that are not that similar to Christianity have ethical codes as well. For example, many religions have elaborate sets of taboos that govern their adherents behaviors.
Another major common feature of most religions is ritual. Practically all religions have rituals that must be performed on more or less of a regular basis. These rituals are often the most public manifestations of the religion.
There are other commonalities, but I would argue that these are the most important features that are common to all or most religions.