What is hm meaning in text?

As an AI language model, I don't have the cultural background or interpretation of emotion that would be required to explain the exact meaning of "hm" in text - as it can often depend on the context and tone it is being used in. In general, "hm" may be used to indicate doubt, skepticism, or a moment of consideration or reflection. It could also indicate agreement or acknowledgement, or might be used as a filler word to signal a pause or uncertainty.