denomination founded in 1901 on Asuza Street in Los Angeles, California. During a time when racism had made its way through Christian denominations and split the faith by skin color, people of all different ethnicities became entangled in love with the birth of the Pentecostal Movement.
Particularly different from other denominations, Pentecostals believe that miracles, signs, and "gifts of the Spirit" are still operational in modern society. The gift that occurs most frequently in Pentecostal churches is glossalalia, also known as "speaking in tongues." Most often manifests itself, not in speaking other human languages, but in speaking in the tongues of angels (1 Corinthians 14:2, 1 Corinthians 13).
Pentecostalism is the fastest growing Christian denomination in the world by conversion and arguably makes Christianity the fastest growing religion. (Islam is the fastest growing religion by birth, but Christianity is the fastest growing by converts.)
There are many different groups within Pentecostalism itself: some which believe in the Trinity, others which deny it and believe in the Oneness of God; some which baptize solely in Jesus' Name (Acts 2:38), and others which baptize in "the Father, Son, and Holy Ghost"; some with very strong standards for women (i.e., not cutting their hair or wearing pants), and others with only standards of modesty.
It should be noted that the Charismatic Movement was birth out of the Pentecostal Movement. While all Charismatics are (consequently) Pentecostals, all Pentecostals are not Charismatics. Popular televangelists like Kenneth Copeland, Benny Hinn, and Creflo Dollar are Charismatics who are teachers in the "Word of Faith Movement." They are not classical Pentecostals.
The Assemblies of God, The Church of God in Christ, the United Pentecostal Church International, The Pentecostal Assemblies of the World, The First Church of Our Lord Jesus Christ, are among many organizations that are classified as Pentecostal.