The purpose of ramdisk_type 1 and 2

I'm running unpack_bootimg --format mkbootimg on a vendor_boot recovery image with header version 4, and it prints these arguments (among the others):

--ramdisk_type 1 --ramdisk_name '' --vendor_ramdisk_fragment out/vendor_ramdisk00 --ramdisk_type 2 --ramdisk_name recovery --vendor_ramdisk_fragment out/vendor_ramdisk01

What's the purpose of ramdisk_type 1 and 2? Why separate ramdisks this way? The recovery image in question is downloadable from here .