A word with several meanings. There are two that most pertain to us in music making. Volume is obviously the most common word used to specify the loudness of sounds. It also pertains to the control on many electronic devices that is used to control the loudness.
In computers and hard drives a volume is a fixed amount of storage on a disk or tape. It is often used as a synonym for the actual storage medium itself, but it is possible for a single disk to contain more than one volume, or for a volume to span more than one disk.