Disk/partition image backup software clones one or more partitions to a VHD [Virtual Hard Disk] archive -- restoring a backup does the reverse, cloning the VHD archive to a real, physical disk or SSD. Normally image backup software can also clone those partitions to another physical drive if you'd rather, and cloning apps like EaseUS Disk Copy are basically limited versions of their image backup tool, Backupper -- it just removes the ability to use VHDs, though you can create your own VHDs in Windows and clone partitions to that as a makeshift backup. While you can clone a hard disk partition(s) to another physical drive to use as a backup, why would you? When you use a backup app, e.g., Backupper, the VHD archives include only data, with no free space, so the single files take up less storage space. So one hard disk/SSD can often store multiple backups, rather than have one cloned backup per drive.
In their ad copy EaseUS claims Disk Copy is faster than alternatives, but I couldn't find anywhere where they back that up, nor could I find any comparisons using Google. When you're copying data from one place to another, copying only raw data is faster than copying individual files, say if you simply copied a folder in Windows Explorer. Beyond that, the speed of the drives matters, as does how they're connected to the PC or laptop, e.g., USB vs. SATA. And USB 4 can be faster than USB 3 which is faster than USB 2 etc. Windows itself has a few ways it can effect the speed of copying, and Macrium Reflect 8 manages to get around some of those bottlenecks to increase copying speed -- the paid version is faster than the free version. And it is possible EaseUS uses similar techniques, though again I couldn't find any evidence saying that was true.
that's a great idea, but if it is not something that can be run from a flashdrive then what good is it if the drive your trying to copy is not bootable?
EaseUS Disk Copy lets you create a bootable USB stick with a copy of the app.
Hard disk/SSD cloning, image backup, &/or partitioning apps normally use drivers to enable VSS in Windows, allowing them to work with copies of any files that are currently in use running Windows. Without VSS the only way to do that stuff would be by booting to an external drive with its own OS. And because those apps install and use drivers, they can't be used portably as-is.
That all said, the bootable USB stick you can create in apps like Disk Copy do not always work, and it can be tricky booting to a USB stick depending on the PC/laptop/tablet you're using. IOW don't take it as an article of faith that once you create that USB stick you're good to go. Test It. Make sure that you can boot to it and that the app on the USB stick runs as it should.