From what I understand there are two fairly distinct major kinds of Buddhism, Theravada and Mahayana.Theravada, the oldest version, is actually quite secular. It's mainly based on the idea that having ambitions and desires is what leads to suffering, and rejects the idea of deities, souls and afterlife. They don't actually believe in literal reincarnation either, rather the "circle of life" which they see as a constant cycle of birth, illness and death which is escaped by achieving nirvana, which basally means to completely abandon the world. They don't worship Buddha either, but revere him as a wise teacher. The closest thing to a 'supernatural' belief Theravada holds is the idea of Karma.Then there is Mahayana, which is what makes up the majority of Buddhists. This form does believe in spirits, and while they do not believe in a creator deity, instead believe that by achieving nirvana anyone can gain omnipotence and omniscience and become a god, and thus worship Buddha as one of an infinite number of deities. They also believe in an infinite multiverse, and that our universe is just an illusion and that the only thing that actually exists is the "Ultimate Reality" which is described as being impossible to describe. The specific traditions and teachings vary widely between regions, but Mahayana is most definitely a religion.