A Ghost image is a compressed single file containing a "snapshot" of the drive you imaged, which can then be stored as a backup of an existing configuration (and restored in case of failure); this can be compared to making an ISO image of a bootable CD -- the ISO isn't readable if you just burn it to disc, but you can burn it as an image file and make a readable CD.
However Ghost also can be made to simply copy a partition exactly to another drive the same way MaxBlast or other tools do, in which case the drive will be bootable (as long as the partition is set to Active, which I'm not sure if Ghost does by default or not). So whether the second drive is bootable or not depends on how you did the backup.