Help with confusion on ROM flash

[m0nti13]

I'm a little confused with the terminology and procedure to using a new ROM version on the Omnia. I always thought of ROM as hardware (Read Only Memory) and when you flash the ROM you flash an entire image.

From what I can gather from some of the threads in here, you seem to be able to flash sections of the ROM? Is this true? Are these what are refered to as bins (binaries?)?

And then what do you need to update the phone's ROM image? because it looks like you can get into trouble if you just use the updated bin(?). You actually need the complete beta image first? then you can update the individual binaries you want?

I understand when people refer to a new ROM, what they really mean is flashing a ROM image, but is there somehow an idea of a partial ROM flash with a binary?

I'm really confused, can anyone shed some light?