Pentecostal Christianity emphasizes the Holy Spirit's activity in believers and communities. Its name recalls Pentecost in Acts 2, when Jesus' followers receive the Spirit and speak in other languages. It is a movement containing many denominations, rather than one church.
Where it came from
Modern Pentecostal movements emerged around the beginning of the twentieth century, drawing especially on revival and Wesleyan Holiness traditions. The 1906 Azusa Street revival in Los Angeles, led by Black pastor William J. Seymour, became an important meeting place and source of worldwide connections.
The movement grew in several places. Local revivals and Christian leadership in other countries also shaped the movement, which cannot be understood simply as an American export. Churches including the Church of God in Christ, Assemblies of God, and Foursquare developed distinctive histories and teachings.
What it emphasizes
Pentecostals expect spiritual gifts to remain active: healing, prophecy, and speaking in tongues, among others. Tongues refers to speech understood as enabled by the Spirit, whether recognizable languages or prayer beyond ordinary speech. Prophecy is understood as a message offered under the Spirit's guidance; churches have different ways of testing it.
Many teach baptism in the Holy Spirit as an experience of empowerment distinguishable from conversion. Some, including the Assemblies of God, teach speaking in tongues as its initial evidence. This is a denominational teaching, rather than a belief shared by all Christians. Other Christians understand receiving the Spirit as inseparable from becoming Christian and differ about the gifts' continuation. Compare The Spirit and spiritual gifts.
Worship and organization
Services often invite expressive singing, prayer, personal testimony, and prayer for healing. Practices vary greatly. Expressive worship often takes place alongside biblical teaching and established forms of leadership. Churches may belong to organized denominations or operate through independent networks. Water baptism commonly follows a profession of faith.
The charismatic movement overlaps with Pentecostalism but also includes people who remain Catholic, Anglican, or members of other traditions. Shared interest in gifts does not make all of them members of Pentecostal denominations.
Differences within the family
Most Pentecostal denominations affirm the Trinity. Oneness Pentecostals, including the United Pentecostal Church International, instead describe Father, Son, and Spirit as ways the one God reveals himself, and baptize in Jesus' name. This is a significant theological disagreement; the broader historic Christian tradition affirms the Trinity. Explore the arguments in Understanding the Trinity.
Pentecostals also differ over sanctification, church leadership, and expectations about healing and prosperity. Promises of guaranteed health or wealth should not be attributed to every Pentecostal church.
Sources & further reading
A question in the margin is a good place to begin.