What 3 gallon mean?

A "3-gallon" measurement typically refers to a volume of liquid equivalent to three gallons. In the U.S., a gallon is equal to 128 fluid ounces, so three gallons would equal 384 fluid ounces. This measurement is often used in contexts such as gardening, where a 3-gallon pot might indicate the size of a plant container, or in water and beverage sales.