For folks who have never come across this, they don't mean that the food is hot/spicy, cold or that it gives you wind. It's more about which type of energy they produce, yin or yang, and the effect that had on the body.
"Heaty food are food that will build you up. Food that will push your body to create internal hot energy (yang energy). Cooling food are food that will push your body to create internal cold energy (yin energy)."