“Boiling” is an adjective and is used to talk about temperature.
We use it to say that something is very hot!
The water is boiling so we can use it to make tea or coffee now!
Boiling is normally related to water. When water is 100 degrees celsius it bubbles and boils. We say that the water is boiling hot. However, we can also use it to describe something else that is very very hot.
It is similar to saying “very very hot”
e.g. It is a boiling day in Barcelona! It is so hot!
e.g. The water is boiling, would you make us some coffee please?
e.g. The sea is boiling today, it’s beautifully warm!