The barrel of oil equivalent (BOE) is a unit of energy based on the approximate energy released by burning one barrel (42 US gallons, 35 imperial gallons or about 159 liters) of crude oil.
The BOE is used by oil, gas and energy companies in their financial statements as a way of combining oil and natural gas reserves and production into a single measure, although this energy equivalence does not take into account the lower financial value of energy in the form of gas.

The barrel of oil equivalent per day (BOEPD) is a unit of energy per time -> production rate of crude oil and natural gas.