The Greek word for tongues is glossa. It can refer to the literal part of the human mouth OR a known language on the earth. It appears 50 times in the New Testament, the majority of which refers to its use for speaking. Examples of these two usages are below.
24. send Lazarus to dip his finger in some water and cool off my tongue (glossa) (Luke 16:24)
9. And they sang a new song . . . (you) did redeem us to God by Your own blood, out of every tribe and language (tongue - glossa) (Revelation 5:9)
There exists only two main parts that discuss tongues speaking in the entire Bible. This article takes a brief look at each of them.
Birth of the church
On every Pentecost, one of God's annual Feast days, Jews from around the known world would flock to Jerusalem. In 30 A.D., the year Jesus died, a small group of 120 of his disciples gathered in the city. Around 9 am the Holy Spirit was given to each person in the group - with attention drawn to this fact by the sound of a mighty wind. Then a manifestation of God's power that could be seen was given through a fire-looking tongue above each person's head.
The disciples gathered received God's holy spirit and then spoke other languages as the Holy Spirit moved them (Acts 2:4). They spoke in KNOWN languages that they themselves had not heard of before! In other words, they took the shortest foreign language course in history!
5 There were Jews living in Jerusalem, religious people who had come from every country in the world (Acts 2:5)
Note that the crowd on this holy day, though all Jewish, lived in a variety of countries. When the disciples began to talk in other languages a crowd naturally gathered to see what was happening. It was very quickly realized by those in the crowd that over 12 different languages were being spoken.
And when word of this went out, the multitude came together and were confounded, because each one heard them speaking in his own language (Acts 2:6)
What the above verse tells us is that the REAL miracle of Pentecost was centered on the ear or hearing! Note that all those present CLEARLY were able to understand all the words that were spoken since the good news of God's kingdom was being announced in the language they grew up with. The next verses in the chapter help us further understand the meaning behind Acts 2:6. The crowd knew the apostles were all from Galilee by their accent (Acts 2:7).
Verse 8 then tells us exactly what was happening.
"Then how is it that we HEAR each one in our own language in which we were born?" (Acts 2:8)
On the holy day of Pentecost God caused a miracle in hearing AND speaking. What took place on this eventful day can be summarized as follows.
Peter gave a message in a language known by those to whom he spoke
Visitors to Jerusalem from around the globe heard, at the same time, the message given in their native language
The listeners of the message asked Peter a question (see verse 37) and received a reply that they heard in the language they grew up with
Nowhere in Acts 2 does it state or imply that tongues speaking entailed making sounds that no one could understand
The Corinthian problem
The church in Corinth was riddled with problems. Paul tackles several of these in both his first and second letter to the church in the city. Their problems included divisions over leaders, taking each other to court, sacrificing to idols, incorrectly taking the Passover, and more! For whatever reason, the church in Corinth was especially amazed and fixated on what today is called speaking in tongues. Paul begins to tackle their problem in this area by stating some of the many ways the Holy Spirit can be manifested in the life of a believer.
"But the manifestation of the Spirit is given to each one for the benefit of all. For to one, a word of wisdom is given by the Spirit; and to another, a word of knowledge according to the same Spirit; And to a different one, faith by the same Spirit . . . and to a different one, various languages; and to another, the interpretation of languages" (1Corinthians 12:7-10, HBFV)
Note something very interesting with Paul's list of gifts. He lists gifts related to languages (tongues) last! This is his way of conveying it relative importance compared to other spiritual gifts. To reiterate his point, a few verses later he lists SOME of the responsibilities and works of service God has caused to appear in his church.
"in the first place apostles, in the second place prophets, and in the third place teachers . . ." (verse 28)
The LAST responsibility listed by Paul is "languages" (tongues - verse 28). The apostle then finishes and sums up his entire discussion.
" . . . and yet I show you a way far surpassing all these" (1Corinthians 12:31)
The gift of speaking in other languages or tongue exists for only a short time and is manifested only when it fulfills God's purpose. After Jesus returns to the earth to reign and rule mankind will again converse in a single language and the gift so touted by many will completely cease.
8 Love is eternal. There are inspired messages, but they are temporary; there are gifts of speaking in strange tongues, but they will cease; (1Corinthians 3:8)