creating a backup plan

I am an online college student and I need some help with an assignment. I was asked to develop a backup plan for a multi server system. The plan needs to include the servers and desktops and to develop a sequencing plan for the tapes. The assignment said I should search the internet for grandparent, parent, and child tape or media sequencing and I can’t find anything. Can anyone either explain these to me or point me to a website that does. I am not wanting someone to do the work for me, but point me in the right direction. Any help would be greatly appreciated.