We believe that tongues are actual languages today. But as was the case in the Bible, they usually cannot be understood by the people speaking in tongues. We know that this was true in Bible days because Paul wrote, 'For he who speaks in a tongue does not speak to men but to God, for no one understands him; however, in the spirit he speaks mysteries' (1 Corinthians 14:2). Paul called this 'praying with the Spirit' (14:14-15). He said that 'he who speaks in a tongue edifies himself' (14:4). To be edified means to be built up and strengthened spiritually. This is what Jude was talking about when he wrote, 'Building yourselves up on your most holy faith, praying in the Holy Spirit' (Jude 20).
These are some of the reasons we believe that speaking in tongues as the Spirit gives the utterance continues to have benefits for believers. We teach that speaking in tongues is the initial sign that a person has received the Holy Spirit. At our church, everyone has received the gift of the Holy Spirit and everyone speaks in tongues. We are a very edified body of believers.
For more on this subject, please see our article 'Speaking in Tongues in the Church,' which you can find on the Doctrine shelf of the Apostolic Free Library on this web site.