comparing 90 Si's wiring to 90 SiR's, how does it work?

[CRXSi90]

hey, ok im looking at this chart (located at http://b16a.honda-perf.org/theswap.html) and it talks about the pin out, the pin outs are #s and letters (ex: A1) as you all probably already know. anyways, are those codes for wires? or how does it work, i mean does A1 stand for a certain wire? im confused please help, hopefully i wont get a "DUH" from any of you, thanks