Pentecostal denominations are Christian groups that emphasize the work of the Holy Spirit and the experience of spiritual gifts, such as speaking in tongues and healing. They believe in a personal relationship with God and often focus on vibrant worship and community involvement. These denominations emerged in the early 20th century, with the Azusa Street Revival in 1906 being a significant event that spread Pentecostal beliefs. Today, there are numerous Pentecostal churches worldwide, including the Assemblies of God and the Church of God in Christ, each with its own distinct practices and teachings.