i really doubt "mbr" will be anything you have to worry or concern yourself about peter but i'll try and explain things as best i can.
first you need to know "mbr" is "master boot record" of a hard drive and is only used on drives formatted in the old dos style partitioning system of hard drives, today from windows 8 on up they don't use the mbr partitioning filesystem any more and use gpt partitioning of hard drives.
the mbr was/is the first few bytes of data on a hard drive that hold the info on the partitioning and which to boot first.
a disc image is exactly that, it will image everything on the hard drive from the first bit of data to the last bit of data.
a system image is exactly the same thing if you only have a single operating system on the hard drive, it will create an image of everything needed to restore that "system"
now the problem your worried about is when you have more than 1 "system" on your pc.
lets say 1 "system" is a windows 7 system and the 2nd "system" is an opensuse system on a separate partition, the bootloader to choose which os to boot to is on the opensuse partition so the mbr holds the data that points to the 2nd partition to boot first, that way when you start the the pc up you are met with options to boot either os.
now from the sounds of it never having used aomei when you restore a "system" image it writes data to the mbr to point to the partition it restored the "system" onto to boot first (windows 7 on first partition in this case.), so in my example you'd lose the option of booting to the opensuse system because the mbr now points to the first windows 7 partition to boot first and not the second where the boatloader with the options to choose which os to boot into is held.
this is overcome by either just imaging and restoring the windows partition alone where the mbr is never touched or doing a full disc image so the original data in the mbr is kept pointing to the 2nd partition.
now in your case i'm pretty sure you use gpt partitions where things work differently so won't run into a boot or mbr problem even if you have multiple os to boot to on a single drive.
more info on mbr vs gpt here :- http://www.howtogeek.com/193669/whats-the-difference-between-gpt-and-mbr-when-partitioning-a-drive/
hope that explains things for you, if not and you have more questions just ask away and i'll try to answer them as best i can.
