IVT is the information for ROM code to locate the image to me memory, which is like jlink use the elf format image.
That make all the segments such as .TEXT as our wish.
That is why called IVT(Image Vector Table). That is what Vector's meaning.

ROM need read that IVT(aslo the boot data) from a special offset.
That is why need put image with a offset.
The reference manual has very very detialed description.