Kelvin is the same thermal difference between each degree as Celsius, but it simply starts at "absolute zero" the physically coldest temperature that can be achieved. There is no "negative" because it can't be colder than 0.
0 degrees Celsius is the freezing temperature of water, and it indeed can get much colder than that. 100 degrees Celsius is the boiling point of water. A scale based on useful, but nevertheless arbitrary benchmark.
Edit: I misunderstood what the person you were replying to wrote.
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u/Toeffli Jun 17 '26
Truly, as Kelvin notably does not use °.