Most people think of it as body language. There’s a lot going on in any conversation that doesn’t happen with words or the meaning of words. There is also content that has to do with the sound of words, separate from any semantic content.
We could have a conversation filled with nonsense words, but the conversation would not necessarily be nonsense. You might think of it as a dance or a sound duet. We would be convening information about how we feel about each other, or our ability to work together, or directing each other’s attention to various places. We might be talking about movement, or, well, an awful lot of other things.
This is stuff that most people pick up without being aware they are even tuning into it. There is also presentation content: what we say by they way we present ourselves physically—the clothes we wear and the make-up we wear and our grooming. There are cultural cues that have to do with the way we use our eyes and hands, etc.
I don’t know how much information transfer is not necessarily contained in our manipulation of symbols, but I would be comfortable guessing that half of a conversation is non-verbal. Maybe someone has researched this and has another estimate. I find that people generally see a lot less going on than I do. But I have dance and musical training, so that might account for why I can get more out of it.
That nonverbal half happens whether the words mean anything or not. So conversations that most people would say are pointless or meaningless are generally far from meaningless for me. But I have a lot of experience in paying attention to these other things and in knowing how to bring them to conscious awareness and interpret them.