* Tone: In some languages, like Mandarin Chinese, the tone you use on a syllable can completely change the meaning of a word. For example, "ma" with a high tone means "mother," but with a rising tone, it means "hemp."
* Stress: In English, we put emphasis on certain syllables in words, changing the pronunciation and meaning. Compare "REcord" (noun) and "reCORD" (verb).
* Intonation: The way our voice rises and falls over an entire sentence conveys different meanings, like a question vs. a statement. For example, "Are you going?" (rising intonation) vs. "You are going." (falling intonation)
So, a supra segmental phoneme is not a single sound like /p/ or /a/, but a feature that modifies the sounds around it.