That's a very poor summary of what prefixes are. My advice, just skip the original article which isn't very good or interesting and read taviso's blog that is l

That's a very poor summary of what prefixes are. My advice, just skip the original article which isn't very good or interesting and read taviso's blog that is linked in the top comment (it gives a few concrete examples of these prefixes). They are modifiers that are part of the CPU instruction.