Speaking in tongues is the free gift which we get directly from the holy spirit when we believe in Him, this happen on the Pentecost day, when the disciples spoke in languages they had not learned, enabling people from many nations to hear the message of God.
Acts 2:4 "And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance."
Speaking in tongues should be done in a good way, we should not abuse it. The apostle Paul emphasized that if tongues are spoken publicly, there should be interpretation so that the church is edified. More important than any spiritual gift is living a life marked by love, obedience to Christ, and the fruit of the Holy Spirit.