What is the difference between flasher and microSD images?

I’m having trouble finding information on the difference between the flasher and microSD images. Why can an image made for microSD not be flashed to eMMC?

The reason I’m asking is because the Debian 9.12 ImgTec image is only available as “microSD”, but I want to run this version from eMMC for performance and reliability reasons. I also want to mount a microSD as a different mount point for writing files. If I flash this image to eMMC, will I run into issues? If yes, is there a way to “modify” the microSD version to work with eMMC?

Thanks in advance.

The difference is one line at the bottom of /boot/uEnv.txt

  If you uncomment the line, the card becomes a flasher image (and if you
don't remove it after the flashing, rebooting will repeat flashing...).

There should not be any 'big' issues, i assumed most customer projects
with 'qt' etc might run out of space on the eMMC..


Thank you for the clarification. I successfully flashed to the eMMC, mounted a FAT32 SD card, and everything works great.