No problem. So, to clarify: when you are setting-up Macrium, there are some options. You will be advised (by the software) that when you set-up the Windows PE boot on your hard drive that you must (like should with an exclamation mark) also set-up a recovery media such as a USB. Essentially, this is a back-up for the PE environment on your hard drive. As another poster said, you would use this to boot-up your computer in the event the hard drive is corrupted.
In the meantime, after you did this initial installation, you are backing-up your hard drive to another drive, either on a schedule or ad-hoc. In my case, I'm backing up an image to a 2 TB Western Digital (WD) drive. BTW, you should always back up complete images, not incremental.
So, something goes wrong and you need to recover. There are two likely scenarios:
a) your hard drive has failed and won't boot from BIOS/UEFI. In this case you would boot from the PE environment on the USB stick. This will load a limited Windows system and at least allow you to assess what is wrong. If you can get to this stage you probably have a corrupted hard drive. There may be other issues, but, for example, if you have a toasted mother board you wouldn't be able to get to this point at all.
b) your windows environment is corrupted due to anything from virus/malware to bad drivers to whatever, but Windows doesn't work. In this case, you will attach your back-up drive to your computer, and when you boot-up you will select the Macrium PE environment on your existing hard drive. Macrium will then install an image from your back-up drive (you select which one, likely the most recent), the computer restarts and life is fine again. Oddly enough, in my experience, the restore actually takes less time than backing-up an image.
I would also like to take the opportunity to advise you not to count on Windows restore points. This is why:
https://support.microsoft.com/en-us/...nstall-updates
Also, I have not had any success with Windows Back Up and Restore using incremental back-ups. The reason Macrium Reflect is so popular is because it works.
Finally, if you have Windows Bitlocker encryption enabled, make sure you have the recovery code backed up in as many places as you can think of. There are other threads on this subject so I'll leave it at that.
I hope this helps.