Pails and Carboys
Pails and carboys are interesting in terms of names because both are considered "drums" per most UN specifications. To break this down into simple terms. Most people when they say pail or bucket mean and open top container with snap on lid or pound on led between the size of 1 to 7 gallons or so.
When people use the term carboy they are often referring to the closed head variety, again all are technically considered drums.