This is as good an explanation of all the tags used to describe the ROMs as I have been able to put together. Please forgive me for any omissions or errors.
STANDARD CODES
[a] Alternate
[p] Pirate
Bad Dump
[t] Trained
[f] Fixed
[T-] OldTranslation
[T+] NewerTranslation
[h] Hack
(-) Unknown Year
[o] Overdump
[!] Verified Good Dump
(M#) Multilanguage (# of Languages)
(###) Checksum
(??k) ROM Size
ZZZ_ Unclassified
(Unl) Unlicensed
[b]SPECIAL CODES
****Gameboy****
[C] Color
[S] Super
[BF] Bung Fix
****Super Nintendo****
(BS) BS ROMs
(ST) Sufami Turbo
(NP) Nintendo Power
****Genesis****
(1) Japan
(4) USA
(5) NTSC Only
(8) PAL Only
[ (B) non USA ]
[ [c] Checksum ]
[ [x] Bad Checksum]
[ [R-] Countries ]
****Coleco****
[ (Adam) ADAM Version ]
****NES/Famicom****
[PC10] Playchoice 10 version
[VS] Vs Version
COUNTRY CODES
(1) Japan & Korea
(4) USA & Brazil - NTSC
(A) Australia
(J) Japan
(B) non USA (Genesis)
(K) Korea
(C) China
(NL) Netherlands
(E) Europe
(PD) Public Domain
(F) France
(S) Spain
(F) World (Genesis)
(FC) French Canadian
(SW) Sweden
(FN) Finland
(U) USA
(G) Germany
(UK) England
(GR) Greece
(Unk) Unknown Country
(HK) Hong Kong
(I) Italy
(H) Holland
(Unl) Unlicensed
STANDARD CODE NOTES
[a] This is simply an alternate version of a
ROM. Many games have been re-released to
fix bugs or even to eliminate Game Genie
codes (Yes, Nintendo hates that device).
A bad dump often occurs with an older
game or a faulty dumper (bad connection).
Another common source of [b] ROMs is a
corrupted upload to a release FTP.
[f] A fixed game has been altered in some way
so that it will run better on a copier
or emulator.
[h] Something in this ROM is not quite as it
should be. Often a hacked ROM simply has
a changed header or has been enabled to
run in different regions. Other times it
could be a release group intro, or just
some kind of cheating or funny hack.
[o] An overdumped ROM image has more data
than is actually in the cart. The extra
information means nothing and is removed
from the true image.
[t] A trainer is special code which executes
before the game is begun. It allows you
to access cheats from a menu.
[!] Verified good dump. Thank God for these!
[b]SPECIAL CODE NOTES
****SNES****
(BS) These Japanese ROMs were distributed
through a satellite system in Japan
known as the Broadcast Satellaview.
They were transmitted along with a TV
show which was connected to the game in
some way. These games were only playable
during the show, and thus stop after an
hour, and many were timed so that only
certain time periods were playable.
(ST) The Sufami Turbo device allowed two
GameBoy sized carts to be plugged into
the SNES. Certain carts combined into
new games much like the Sonic & Knuckles
lock-on technology by Sega.
(NP) Nintendo Power has been known to release
games only available to its subscribers.
Most of these ROMs are Japanese, as this
practice occured mainly in Japan.
**** Genesis ****
(1) Carts with this code will run on both
Japanese and Korean machines.
(4) While this code is technically the same
as a (U) code, it is a newer header
format and represents that the cart will
run on USA and Brazil NTSC machines.
(B) This country code indicates that the
cart will run on any non US machine.
[c] This code represents a cart with known
faulty checksum routines.
**** GameBoy ****
[BF] Bung released a programmable cartridge
compatable with the GameBoy which could
hold any data you wished to play.
However, many games do not function on
Bung v1.0 carts and have to be 'fixed.'
**** Nintendo ****
[PC10] The PlayChoice 10 was an arcade unit
which played exact copies of NES games
in an arcade cabinet. The machines had a
choice of 10 games to choose from and
ran for about 3 minutes on 25 cents.
[VS] The Versus system ran on similar hardware
to the PC10 machines, but simply allowed you
to play against each other.
Credits must go to everyone who contributed to this.