# What is the relationship between boiling point and pressure?

The boiling point of a liquid are the conditions of temperature and (ambient) pressure when 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 $\text{1 atmosphere}$.
It follows when we reduce the ambient pressure, the boiling point of the liquid should reduce. And this is the principle of vacuum distillation: if the pressure is reduced, an otherwise involatile liquid may be distilled at a reduced temperature (compared to its $\text{normal boiling point}$.
For more details, and I don't know at what level you are, you might want to look up the $\text{Clapeyron equation:}$ https://en.wikipedia.org/wiki/Clausius%E2%80%93Clapeyron_relation