The link description was all I could think of to make this more digestible and as close to the truth as possible. I think it's technically called making a assembly symbol global and then linking that object file to a C file that is including the object file and using the symbol name, though I'm not sure.

Also why? I'm interested in writing something in 16 bit 80236 compatible assembly, assembling it, writing a wrapper function in C to call the asm object code, compiling it as a free-standing binary with no stdlib support. Sending those raw bytes to a floppy disk to be read in by my stage-1 bootloader; just to see how hard and if I can. More importantly to me, to get a list of references for where this tribal knowledge seems to have gone because OSDEV seems to have zilch for it other than a hand-wave of an explanation.