speaking a real language that is different from your native tongue is what Speaking in tongues, as taught in the Bible is.
A tongue simply refers to another known language , It is not a mysterious or invented sound.
when they spoke, people from different nations heard them clearly in their own native languages even though the apostles were Galileans , this can be seen In the book of Acts.
the listeners were amazed because the words were understood without confusion.
biblical speaking in tongues involved real languages spoken by people on earth, this is what this shows.
the power of the Holy Spirit for understanding and communication made thsi possible .
Today, many groups use sounds that do not belong to any known language and they claim to speak in tongues.