Tongues

Imagine being in a crowd hearing several different languages spoken from faraway lands, feeling left out, confused, and so unsettled that you're about to leave. Suddenly, you start to understand someone speaking in your own language, so you decide to stay and get closer so you hear more clearly what they're saying. You are amazed at what they are saying, so you get closer to see who is speaking. Then you see the person is a foreigner so you listen even more closely. Other people don't understand and think that they're lunatics. Being filled with the spirit, they were speaking in a different language that their friends didn't understand so their friends thought they were drunk.  But no, you know that they're not crazy because you can understand them speaking sanely in your own language!

This is what happened at Pentecost. 

"Tongues" is just another way of saying ... foreign languages that you don't understand... like French, Greek, and Hebrew.