What is the gift of tongues?

Some believe the gift of tongues involves a heavenly prayer language for the purpose of talking to God and/or edifying one’s own self. But Scripture teaches us that tongues involves sharing the Gospel in foreign (human) languages for the purpose of evangelism (Acts 2:8). 1 Corinthians 14 is actually encouraging believers not to abuse their missionary gift of tongues by bringing it into the church service and speaking in a mysterious way that only God understands.