What exactly is ORG directive used for?

[ben321]

I know it sets some origin of the program, but is this used by NASM for calculating offsets when using other compiler directives (such as SECTION .mysection start=0x1234) where the value of ORG is then added to the offset specified in the other directive, or is the value specified with ORG actually used for calculating offsets used in actual opcodes (such as JMP, CALL, MOV, etc) that access memory locations?

[Bryant Keller]

ORG sets the origin of the object file (where the file is expected to be loaded into memory) when compiling the code as a flat binary. This adjusts the program counter for working out the addresses of labels during assembly.