Acts 2 - spoke with other tongues (languages)
What actually happened at Pentecost in this matter of the apostles "spoke with other [gr. heteros] tounges (languages)?
Acts 2:4–14 (KJV 1900)
And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
And there were dwelling at Jerusalem Jews, devout men, out of every nation under heaven.
Now when this was noised abroad, the multitude came together, and were confounded, because that every man heard them speak in his own language.
And they were all amazed and marvelled, saying one to another, Behold, are not all these which speak Galilaeans?
And how hear we every man in our own tongue, wherein we were born?
Parthians, and Medes, and Elamites, and the dwellers in Mesopotamia, and in Judaea, and Cappadocia, in Pontus, and Asia,
Phrygia, and Pamphylia, in Egypt, and in the parts of Libya about Cyrene, and strangers of Rome, Jews and proselytes,
Cretes and Arabians, we do hear them speak in our tongues the wonderful works of God.
And they were all amazed, and were in doubt, saying one to another, What meaneth this?
Others mocking said, These men are full of new wine.
But Peter, standing up with the eleven, lifted up his voice, and said unto them, Ye men of Judaea, and all ye that dwell at Jerusalem, be this known unto you, and hearken to my words:
The apostles spoke in languages which apparently were understood by those devout Jews who were present at Jerusalem for the feast of weeks (Jews from both Jerusalem and Judea as well as places from the diaspora (both eastern and western regions) ... which dialects of which languages did these Jews speak and understand? were those their different dialects of Aramaic (spoken in eastern areas) and Greek (western areas)?
Did the apostles speak those languages (which were actually languages they knew how to speak)? Cp. v.14 and Peter's speech ... it was understood by all but obviously not spoken in a dozen or so "foreign languages" which Peter himself did not understand ...
In which regard were the languages spoken by the apostles "other [gr. heteros = "different in kind"] languages? Other than what??
Obviously, the large crowd was not gathered in a small house, but - indicated by the reference to the "3rd hour / an hour of prayer" - in the temple area. Could it be that the totally astonishing thing was that these common people dared to speak of the mighty deeds of God in their "common" language rather than in the so-called "holy language" Hebrew that was "proper" to be used in the temple and which was "properly" used only by the priests serving at the temple ???
Peter's reference to Joel also indicates that common folks (and not just priests) would be filled with holy spirit and speak or declare God's word powerfully in the last days ... which was fulfilled in what happened there.