RE: copy/backup
The other difference is that once you've sent your copy to him, you still retain the original. So the publisher missed out on the chance to sell another copy of their material.
Backup is a little different. Assuming that you are not using both copies at once (i.e. on a CD player at home, and another in your car), the backup enables you to continue to use the material that you purchased.
Many of the drawings in MR carry the statement/release that the purchaser can make copies for his own use (presumably so you don't have to chop up the magazine). However, this does not extend to making copies for someone else, due to the reason in my opening paragraph.
Andrew