https://youtu.be/_g1vYKuw8xw?si=O5Q7AMtf4TPaLEyz Speaking in tongues is a spiritual gift, were you speak in different languages that no one have thought you before, in new testament it was written that speaking in tongues is a miraculous ability that will happen to you if the holy spirit descend on you and before the holy spirit descend on you, you must be a believer, for example at the day of the pentecost in the book of acts 2 when the desciples started speaking in different languages which was the first recorded instance, and people from different nation's had their voice.
In the book of 1 Corinthians 12:4 the apostle Paul said that speaking in tongues is one of the spiritual gift given by the holy spirit, and also said that interpretation is very important were there is a gathering so that everyone will understand the message.
The purpose of the gift is a way for believer's to praise God, to communicate when there is a language barrier and also to build up the church. Some religion said that this speaking in tongues gift came from the modern church, while others believed that the modern church are just following the footsteps of the old.