Speaking in tongues in the Bible happens to Peter and his eleven companions in Jerusalem. They were preaching the Word of God in their own Galilean language to the Jews and devoted men who visits Jerusalem. As they preach using their own language, the Jews and visitors who listen to them hear it in their own language and they were amazed.
Act 2:5-11 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.
Nowadays, many peoples pretend to speak in tongue but it can NOT be understood. See what the bible say about them...
1Co 14:9 So likewise ye, except ye utter by the tongue words easy to be understood, how shall it be known what is spoken? for ye shall speak into the air.
God bless you all.
:shout