Pentecostal origins go back to the first indwelling of the Holy Spirit after Jesus returned to heaven. The believers met and prayed for 40 days and suddenly the Holy Spirit came upon them and indwelled them. They rushed into the streets and witnessed to people in their own languages, suddenly able to speak in other languages. Other references are given in the New Testament about the ability of some to speak in tongues in prophecy, requiring another person to interpret the meaning. Today, Pentecostals believe in a sudden, dramatic indwelling of Christians by the Holy Spirit.
Some Pentecostals believe in handling snakes, faith healing and exorcisms.
Pentecostals can be found in a variety of denominations and form a sub-group of these denominations. An interesting article on the indwelling of the Holy Spirit Non-denominational churches offer an open door opportunity for people to attend a worship service and develop a fellowship with others without having to decide on specific beliefs. It can be seen as a rejection of the organized religions which, over the years, have become so organized as to lose touch with the essence of Christianity, so some non-denominationals are attempting to get back to the Scripture basics. Others are more watered-down approaches to religion. The beliefs are reduced to the lowest common denominator - belief in God, perhaps Jesus, fellowship with a loving forgiving God, etc.