What is boiling? When does a substance boil?

$\text{The boiling point}$ is defined as the temperature.......
The $\text{boiling point}$ is defined as the temperature at which the vapour pressure of the liquid is equal to the ambient pressure, and bubbles of vapour form directly in the liquid. The $\text{normal boiling point}$ is specified when the ambient pressure is $1 \cdot a t m$.
Of course, if we reduce the ambient pressure, the boiling point will be substantially reduced, and this is an example of the principle of $\text{vacuum distillation}$, where an otherwise involatile liquid is distilled under high vacuum.