The broadest definition of paganism is “any religion not in the Abrahamic tradition” – in other words, anything not Jewish, Muslim, or Christian. This broad definition includes established religions like Hinduism, Buddhism, and Shinto as well as tribal religions around the world. It also includes a vast array of “new religions” like Voodoo, Santeria (sort of), Wicca, Aasatru, Strega, Druidism, and many others.
A more commonly used and narrower definition is “religions in the Neopagan tradition”. This definition excludes most of the religions included in the broader definition. The religions included under this definition include Wicca, Aasatru, Strega, and Druidism, among others. It generally does not include tribal religions, long-established religions, or African diaspora religions.
The most common religion referred to as paganism is Wicca, but the definition is definitely broader than that. Although some people use paganism and Wicca interchangeably, this is incorrect. While Wicca is a very popular pagan religion, it is far from the only one.