Do Pentecostals believe that they are speaking real languages or that God purposely uses gibberish? How do Pentecostals reconcile the babbling of modern "tongues" with the scriptural example of actual languages being spoken? Do they say that the babbling is indeed a real language or that God has chosen now to use babbling for other purposes than to edify by communicating actual messages? In other words, do they teach that the ecstatic incoherent sounds are now the divine order or do they say that what appears to be repeated meaningless pseudo-lingo is actually a real language?
I've heard at least two lines of thought on the issue back when I was in the Charismatic movement, attending Full Gospel churches etc.


A minority of folks seem to cite the verse of saint Paul that mention "the tongues of Angels" and claim it as a kind of heavenly language.
Romans 8:26:


  In the same way, the Spirit helps us in our weakness. We do not know what we ought to pray for, but the Spirit himself intercedes for us through wordless groans.  


The majority however see this as being a proof text for modern glossalia being "gibberish", most of the time.   However many Charismatics will point out many anecdotal tales where people who believe they are just speaking the groans of the spirit/gibberish are in fact speaking actual languages that they never studied!   (There is someone in the congregation that studied the language that recognizes the speech as being a language in an ancient or modern tongue and can even translate the message, which is often a praise to God or some other similar message.)