[MikeHolman]

IR is usually represented as a sort of linked list of instructions where you can easily move around instructions, add/remove them, and replace higher level instructions with lower level instructions as you go through compiler passes. At the end, the IR is a linked list of machine instructions, which gets written out to a code buffer as the last step.

Bytecode is usually a buffer of high level instructions that is compact and fast to read (for the machine). Good for interpreting and holding the semantics of a program in a format that is more efficient than the source code, but it is usually not a good format for running compiler passes.