This file is the sole container for from every game you play on that memory card slot. If you have 10 different PS1 games saved on Slot 1, every one of those save files resides inside epsxe000.mcr . Losing or corrupting this file means losing every one of those saves simultaneously.
For individual game saves, use MemCardRex to export each game’s block as a separate .mcr or .psx file. epsxe000.mcr