It is installed by the package shim-x64-15.8-3.x86_64. It is the default boot loader if you select the disk device in the uefi boot menu.
It works together with /boot/efi/EFI/BOOT/fbx64.efi to find the grub loader and install the boot entry into the uefi boot menu using the /boot/efi/EFI/fedora/BOOTX64.CSV file.
Other OS will probably install its own version of /boot/efi/EFI/BOOT/BOOTX64.EFI, so on a Micorsoft system it will be the WIndows loader instead of the shim. Also, if you install sd-boot. then BOOTX64.EFI will be a copy of the sd-boot loader.