This is a tricky topic, but there is such a wide spectrum of understanding (and acceptance) in regards to tongues, but I will tell you what I think Paul might be trying to say to us. My understandings of what tongues practically is is a muttering of sounds that express something the Spirit is saying to me that I just don't have words for. Have you ever felt like you wanted to scream because you were either so thankful or so desperate? Sometimes people want to just hit things, cry or yell - but often there just aren't words to describe the emotions. Sometimes I think tongues can be like that - where there's something you want to pray to God, but you're not sure you have the words to pray it so the Spirit prays for you. I don't think it necessarily has to be overly emotional, that was just for the example's sake.
However, I think Paul was recognizing that since we are human, it's hard for us to know what to do with something that's wordless and formless. He wasn't discounting the process of praying wordless prayers through the Spirit, but that it's good to find words from our understanding to use. When we use these words to describe what we want to pray for, those around us can identify it and agree in prayer with us. This brings us together in unity.
This is a small perspective on the topic, but I challenge you to ask God for even more understanding of tongues and the spiritual gifts! It can be a scary topic, because it's hard to know if it's important or if we should just avoid it since we don't understand. But I believe God always loves when we move past our fears and ask Him for His help. So ask Him and see if you think He tells you anything (write it down).
Lord, thank You that there are depths of knowledge to gain about You! Please grow us in Your knowledge and remove all fear that You won't speak or that You'll say something we don't like. We trust You and love You. Amen
- Logan Johnson