A 'tongue' is a language. A living language is speech which is understood by at least two or more people. A dead language is not spoken by anybody any longer.
I speak in tongues, I speak several languages - English very well, Norwegian quite well, Swedish sort of, German and French a little, and smatterings of other languages like Malay.
Every tongue or language has a vocabulary, grammar and syntax that can be systematically learned or taught. We use language to contemplate the deep mysteries of life.
Animals cannot do this. Humans are the only living creatures that speak a known language of this kind.
When the Bible speaks of 'tongues' or 'languages' it always refers to what I have been saying here. It never means gibberish or nonsense. Just as we in English have various words to describe meaningless sounds (e.g. gibberish, nonsense), so too do Hebrew and Greek.
Whether our native tongue which we know well or a foreign tongue which we have not yet learned which may SOUND nonsensical to us (in English, we often say of such a language, 'It's double Dutch' or 'It's all Greek to me'), that 'nonsense' is, in fact, a true language with vocabulary, grammar and syntax which can be systematically taught and learned. In Greek this is called GLOSSOLALIA from which we get the English word, a 'Glossary' which is a list of words and their meanings or explanations.
Glossolalia NEVER means actual gibberish or nonsense for which there is a special word in Greek: BATTALOGEO. Battalogeo has no vocabulary, grammar or syntax. Babies making random sounds or Pentecostals/Charismatics speaking gibberish is BATTALOGEO - they are not speaking LANGUAGES or TONGUES, whether understood or foreign.
When in Acts 2 the disciples spoke in GLOSSOLALIA on the first messianic Day of Pentecost (Shavu'ot), they SUPERNATURALLY spoke KNOWN (to them) and UNKNOWN or FOREIGN (to them) LANGUAGES or TONGUES for the benefit of believers in Yahweh from all over the Roman Empire. They did not speak BATTALOGEO or GIBBERISH. They were perfectly understood by those whose languages they were speaking. No interpreters were required because the purpose of speaking tongues supernaturally like that was to convince the listeners that Elohim/God was with the first Christians. And when they did this and spoke PROPHETICALLY at the same time, their listeners were converted to Christ!
The same thing happened in Acts 10:46 to some Gentiles in Caesarea when Peter and some disciples were in the home of a Roman centurion called Cornelius, who had invited some friends along. Peter specifically declared that this was what had happened to them earlier, referring to Jerusalem at Pentecost (Acts 10:47). And though the languages and dialects are not listed in this second supernatural repeat occurrence, that there were several is implied as Caesarea was a Roman garrison with soldiers and administrative staff from all over the Roman Empire who would have spoken a variety of languages in addition to Latin or Greek.
On both occurrences Elohim/God was showing that through the gift of the Ruach haQodesh/Holy Spirit given to the first Christians/Messianics, that He was reversing the curse pronounced at Babel as now all believers could understand one another. Later, in Corinth and elsewhere, Elohim/God called INTERPRETERS to supernaturally translate these various languages/tongues so that the whole of a congregation could be edified by the prophetic pronouncements given in polyglot assemblies such as Corinth. For Corinth in Greece was, like Caesarea in Israel, a cosmopolitan Roman colony. Both were important trading ports.
The gift to speak or interpret foreign languages or tongues, like other listed gifts in Scripture, was given by Yahweh to only a few select believers in a congregation, never to everyone. It was never a 'heavenly language' in the sense that it was a new language no one had ever heard before. It was not a special angel language given to humans for such was not needed. Angels, as supernatural beings, speak all human languages.
When, one day, heaven and earth converge and unite as one in the RESURRECTION, those who are resurrected will be able to communicate in all languages, naturally, like the angels, and even telepathically. In the Millennium resurrected and unresurrected persons will mingle and many languages still be spoken. But at the end of the Millennium, when the earth is totally transformed, everyone will speak or telepathically communicate one language. No one knows what language that will be, nor do we need to know.
If you speak gibberish, whether as a child (mere dissociated speech) or supernaturally (demonic) in a Pentecostal or Charismatic setting, or even privately, then in the case of the latter you are speaking falsely. Indeed, you are not even strictly speaking, even 'speaking' - what you are doing is creating disorder and chaos, and Yahweh is not the Elohim/God of disorder, for "Elohim/God is not an Elohim/God of disorder but of peace, as in all the meetings (assemblies, churches) of Elohim's/God's holy/set apart people" (1 Corinthians 14:33). Because BATTALOGEO is disordered nonsense, most who utter this false 'tongues' cannot control themselves and break Paul's instructions to speak in turns and no more than 2 or 3 people. They all speak together in a mass of anarchy and confusion. They are disorderly and reflect the chaos of hell, not the order of Heaven.
If you are confused about what the Bible teaches about tongues/languages/glossalalia, please see the many articles on the Tongues website: