Mageia forum

How about an explanation of the bottom 3 items?

The 1st 4 I understand.

Thanks.

Boot Mageia 4 == "Load Mageia with latest installed kernel".
Bottom 3 items allow to load Mageia with kernel from item's name. So, "desktop 3.12.8-2.mga4" mean "Load Mageia with 3.12.8-2.mga4 desktop kernel".

So, kind of an undated automatic back-up??

Not at all.
When you install new kernel package (for example, you receive it with updates) old kernels doesn't removes. So, if you will have troubles with new kernel, you able to load Mageia with previous kernels by additional items in boot menu (bottom 3 items on your screenshot).