Religion is also the general term applied to a belief system. For example, Christianity is a religion whilst Roman-catholic, Protestant, Orthodox describe different forms of the same religion. In contrast to this, Christianity and Islam are two different religions.
Religion is and was a transcending factor for the development of the arts, especially for the visual arts and literature. Many works of art can't be understood fully without knowledge of the religion that has influenced it. One good example is art in the Islamic context. As Islam, the religion, forbids the depiction of humans and animals, Islamic art has developed into a highly abstract form that includes floral, geometric and arabesque elements. Religion becomes so an inherent part of culture.
Religion in our everyday language often refers also to 'world religions', the main belief system people adhere to. These can be divided in the 'abrahamic or book religions' that encompass Christianity, Islam and Judaism, together with Baha'i and Rastafari. Indian Religions, i.e. Religions that have evolved on the Indian subcontinent (Hinduism, Buddhism, Sikhism, Jainism). Religions of the Far East (Taoism and Confucianism) and a wide range of different tribal religions. The majority of people today belongs either to an Abrahamic or Indian religion.
Religion, in summary is the organized form of personal faith, tightly woven into the cultural context it has evolved from and that it influences in return.