Although a Christian holiday, Pentecost isn’t widely celebrated outside of the church like Easter and Christmas are, notes PBS. And not all denominations observe it, reports the Christian Post. But many congregations do, including the Catholic and Eastern Orthodox churches. These churches put together particular messages on the seventh Sunday after Easter. (The date for Pentecost varies because of the fluctuating dates for Easter.)

Some congregations also hold a feast or focus on teaching about the event from the Book of Acts. Ray Pritchard explains, “Modern Christians observe Pentecost as a holiday, not to celebrate a wheat harvest, but to remember when the Holy Spirit invaded the Church in Acts 2” (via Crosswalk). Notable differences exist when it comes to how modern-day Christian churches interpret the significance and meaning of Pentecost.

For example, Catholicism recognizes Pentecost as a “distinct holiday.” But members of the Eastern Orthodox church consider it the final day of Easter and conduct ceremonies accordingly. Messianic Jewish and Christian congregations, which observe traditional Jewish festivals within the context of Christianity, observe Shavuot and Pentecost together, asserting all believers are “bonded together not by rules, but by the Holy Spirit within them” (via Jews for Jesus).

The effects of the Azusa Street Revival would be felt across the United States and worldwide, per Pew Research Center. Many movements and churches sprang from this revival, including the Apostolic Faith of South Africa and the rise of popular religious figures and faith healers. Among the most famous were Aimee Semple McPherson, Kathryn Kuhlman, and Oral Roberts (via Way of Life Literature).

Of course, a serious downside to all of this also existed. The Pentecostal movement soon earned a reputation for aiding and abetting hypocrites and swindlers. These included preachers like Charles Fox Parham, Jimmy Swaggart, and Jim and Tammy Bakker. The first scandal in Pentecostalism came with Parham, arrested for soliciting a young man (some say teenager), per The Messed Up Church. Even more shocking, a series of violent exorcisms by his followers ended in death, known as the so-called Parhamite Killings.

And who can forget about Jimmy Swaggart’s very public “fall from grace?” There was little wiggle room after photos emerged of the famed preacher with a sex worker outside a shabby hotel in New Orleans, Louisiana, per Greensboro. Famed televangelists Jim and Tammy Faye Bakker also shocked the nation with egregious financial and sex scandals (via ABC News). Pentecostalism came under heavy scrutiny because of these criminal shenanigans.

Hypocritical church leaders and bizarre practices in the Appalachians gave many Pentecostals the equivalent of an “inferiority complex.” Or, as one Bible student put it, “They felt as if they were the weird uncle of modern Christianity” (via Christianity Today). But today, many Pentecostal beliefs have gone mainstream and are now incorporated into common worship (like hand raising). According to the Study of Global Christianity, Pentecostals account for a quarter of all Christians.

Why does Pentecostalism account for such a large number of believers? Scholars have put forth various arguments. But many agree that Pentecostalism proves both sensational and exciting. In other words, “it touche[s] the senses of its adherents,” bringing them into a more profound walk of faith. That said, many leaders within the movement would like to move past sensationalism into a deeper and more mature faith. While they might focus on the manifestation of the Holy Spirit through speaking in tongues, they eschew other aspects (such as handling snakes or drinking poison).

If you remove the most salacious associations from the picture, there are many beneficial things that Pentecostalism has contributed to the Christian faith. For example, it has placed a strong emphasis on reinvigorating missionary work, reintroducing the concept of spiritual gifts to Christianity, and more. According to How Stuff Works, Pentecostalism is one of the fastest-growing religious denominations in the world.

More and more Christians worldwide have embraced many tenets of Pentecostalism, from Holy Spirit baptism to speaking in tongues, per the Acton Institute. Yet, they don’t always identify as Pentecostals. Instead, some groups now call themselves “Spirit-filled” or “Spirit-empowered.”

Why move away from the term “Pentecostal”? Because of how loaded it can be. What’s more, it has deep associations with the U.S., and more particularly, the Appalachians (via Appalachian State University). For this reason, many international Christians don’t feel the label suits them. And as for Charismatic versus Pentecostal? According to Christianity Today, the term refers to a movement in the 1960s and the 1970s where people from various denominations received the baptism of the Holy Spirit yet stayed in their original churches.

As for international believers? Many don’t feel distinct ties to events such as the Azusa Street Revival. While they may believe in the power of the Holy Spirit and baptism, they don’t identify with either of the terms “Charismatic” or “Pentecostal.”

Christian churches today remain widely split when it comes to speaking in tongues, prophecy, and healing through prayer and laying on hands. Yet, it’s impossible to argue that these weren’t facets of the early church in the Book of Acts (via Crosswalk). Did these miraculous happenings come to an end once the church gained in membership and following? That’s a question that Pentecostals, Charismatics, and Cessationists will continue to argue.

On the one hand, many mainstream denominations strongly discourage believers from babbling in foreign or unknown languages. Believers who speak in tongues may even get expelled. On the other hand, churches with a Pentecostal or Charismatic bent don’t believe followers have received the baptism of the Holy Spirit until they manifest this gift, according to ABC 13 News.

These Christians describe speaking in tongues as a very personal experience involving communicating in spiritual or angelic languages that only God and the heavenly host can understand. But what does science have to say about the matter? Dr. Andy Newburg studied brain scans of people speaking in tongues and found that the part of the brain that controls speech wasn’t active when these participants were speaking in tongues (via ABC 13 News). What does this research mean in the broader context of Pentecost? It’s hard to know. But it adds another layer to a fascinating phenomenon in the Judeo-Christian tradition.