Speaking in "tongues" is not a language of some people here on earth as it was at Pentecost. Are today's tongues biblical?
In the Greek, the word translated as tongues is glossalalia, meaning the literal tongue or a language. When the gift of tongues (speaking in foreign languages) was first given at Pentecost, we know these languages were definitely understood by foreigners. Act 2:7-8, 11 (NIV), “Utterly amazed, [...]