What occurs when the vapor pressure of a liquid is equal to the atmospheric pressure?
Boiling & Pressure dependency
When the system is open to atmosphere and the above mentioned condition occurs then the liquid starts boiling.
If you've a closed system or isolated system, this will not have any effect other than increasing vapor amount in the system. The boiling will occur only when the vapor pressure becomes equal to the total pressure of the system.
When water is boiled with open lid it will boil at