Difference between /dev/st0 and /dev/nst0

I use a SCSI tape drive to perform backup of data and the drive has a generic device name of /dev/st0. /dev/st0 always go back to the beginning of the tape after performing operations. Based on this feature, /dev/st0 only allows one archive to be be created (tar cvf /dev/st0 data) and all subsequent data must be added to the single archive by appending new data using the syntax of “tar rvf /dev/st0 newdata”. How about multiple archives on a tape ? The answer is /dev/nst0 which will not rewind tape to the beginning, thus new archives can be created one after the other.