The RAID system stores the same data redundantly on multiple disks that nevertheless appear to the operating system as a single disk. Although JBOD also makes the disks appear to be a single one, it accomplishes that by combining the drives into one larger logical one.
JBOD means the individual disks are presented (to a server) with no amalgamation, pooling or structure applied. The term is in widespread use, especially in the context of computers that have software volume management, such as LVM (AIX, HP-UX, Linux), DiskSuite (Solaris), ZFS (Solaris), Veritas Volume Manager (UNIXes), Windows, and so-on.
Spanning or concatenation is an additional configuration that can be applied by volume managers to combine JBODs into larger logical volumes or LUNs (logical unit numbers).