the Celsius scale
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The Celsius scale is the everyday temperature scale used across most of the world for weather, cooking, and body temperature. It is built around water: at standard atmospheric pressure, water freezes at 0 C and boils at 100 C, and the space between is divided into a hundred equal degrees (its old name, 'centigrade,' means 'hundred steps').
A Celsius degree is exactly the same size as a kelvin, so the two scales are just shifted versions of each other: T(C) = T(K) - 273.15. This also means a temperature difference is numerically identical in both; a rise of 10 C is a rise of 10 K. Celsius is the standard for everyday use, while physics equations that need an absolute temperature use kelvin. The scale is named after the Swedish astronomer Anders Celsius.
Do not confuse Celsius with Fahrenheit, the scale still common in the United States, on which water freezes at 32 F and boils at 212 F. And note that although 0 C is a convenient reference (freezing water), it is not a true zero of temperature: colder temperatures, all the way down to -273.15 C, certainly exist.
Human body temperature is about 37 C, a warm bath about 40 C, and a hot summer afternoon about 35 C, all comfortably described without ever needing a negative number.
Celsius anchors on water: 0 C freezing, 100 C boiling at standard pressure.
0 C is not absolute zero: it is just the freezing point of water, and genuine temperatures continue far below it, down to -273.15 C.