"Oneness Pentecostalism" began in 1914. At a campmeeting of the Assemblies of God, pastor Scheppe claimed that it had been revealed to him during the night that baptism must be done in the name of "Jesus Only"-hence the nickname of "Jesus Only" Churches that is sometimes used for Oneness Pentecostalism.
They don't believe in the traditional idea of the Trinity/Godhead. They believe that God is one person and the names Father, Son & Holy Spirit are titles. The title "Father" refers to a parental relationship, the title "Son" to His humanity & divinity and "Spirit" refers to His activity.
They also believe in a strict lifestyle, baptism by the Spirit (speaking in tongues) as an indication of your salvation. Oneness Pentecostals do not baptize in the name of the Father, Son & Holy Spirit... rather just in the name of "Jesus".
One of the largest Oneness denominations is the United Pentecostal Churches International.
Some claim that Oneness Pentecostalism is a CULT...Are they? ---NO... people throw that word around a little too much over differing views of doctrine. Are Oneness Pentecostals Wrong? -YES, about glossolia (gibberish speaking in tongues), so-called Spirit baptism as a sign of salvation and of course on their view of the Godhead/Trinity. But that does NOT make them a CULT...
Of course one should NOT be involved in their false doctrines - Thou shalt not sow thy vineyard with divers seeds: lest the fruit of thy seed
which thou hast sown, and the fruit of thy vineyard, be defiled.
Deuteronomy 22:9
Oh, and BTW, Go ye therefore, and teach all nations, baptizing them in the name of the
Father, and of the Son, and of the Holy Ghost:
Matthew 28:19