This is the 995th most frequent Italian word.
caldo
"Caldo" means "hot" or "warm."
Here, 'caldo' is used as a noun to describe hot weather conditions.
Oggi fa molto caldo, ideale per andare al mare.
Today it's very hot, perfect for going to the beach.
In this sentence, 'calda' (derived from 'caldo') is an adjective modifying 'chocolate', to describe a warm beverage.
Mi piace bere una cioccolata calda durante l'inverno.
I like drinking hot chocolate during the winter.
'Caldo' in this context functions as a noun to comment on the high temperature in the room.