I found this in an FAQ file on Gamespot:
-> The plus and minus signs represent the release rate. By clicking the
corresponding button, you can either increase or decrease it. Recall
that you can't put it below the initial speed for that level, nor can
you put it above 99.
-> CLI stands for Climber. When applied to a Lemming, that Lemming will
take on the ability to scale walls. This ability lasts until the end
of the level.
-> FLO stands for Floater. When a Lemming who is a floater falls from a
large distance, it will deploy a parachute-like umbrella that allows
them to fall any distance without splatting. Like the ability to
climb, this lasts until the end of a level.
SPECIAL NOTE: When a Lemming has both the ability to climb and float, it
will be labeled an Athlete by the game. I use this term as well, so it
would be a good idea for you to learn it as well. An Athlete is just a
Lemming that is both a climber and a floater.
-> BOM stands for Bomber. Any Lemming that is made a bomber immediately
affects a five-second fuse. Although usually applied to blockers,
situations do arise where you will have to make walkers into bombers
as well. At the end of the five-second fuse, the Lemming blows up.
Generally, you should try to use as few that you are given as you
can. Lemmings can't bomb through steel under normal circumstances.
-> BLK stands for Blocker. Any Lemming that is made a blocker is frozen
in place semi-permanently (special situations sometimes make blockers
into walkers). Any walker or other Lemming that runs into a blocker
will turn around and go in the other direction. Blockers are not
always available to you or cannot be used in the interest of saving
enough Lemmings, so creative ways of encasing groups of Lemmings may
sometimes have to be found.
-> BLD stands for Builder. One builder can construct a 45-degree bridge
comprised of twelve tiles. If you have sound effects on, you will
hear a clicking when a builder is about to run out of tiles, in which
case you need to listen should you have to keep building a bridge.
I would consider builders the most common task assigned to Lemmings,
so they play a very important role in getting Lemmings to the exit.
-> BSH stands for Basher. Bashers punch through walls in a horizontal
line until they get to the end of the wall. The other Lemmings can
then walk through the narrow tunnel that the basher makes. Lemmings
can't bash through steel under normal circumstances.
-> MIN stands for Miner (not the under-18 kind - like a coal miner).
With pick-ax in hand, a Lemming will mine a diagonal tunnel downward
in the direction it was facing when you clicked on it. Lemmings can't
mine through steel under normal circumstances.
-> DIG stands for ... well, Digger. Any Lemming turned into a digger
immediately takes to digging a tunnel straight down through the
terrain below it. Lemmings can't dig through steel under normal
circumstances.
-> PSE stands for Pause, which in this game has an icon that looks like
a tiny set of paws. (Get the joke? Yeah, I know, it's bad.)
-> NUK stands for Nuke. This is to be used in situations when no more
Lemmings can possibly be saved or when you feel like looking at a
thoroughly amusing pyrotechnic displays on days other than the Fourth
of July. When you double-click this button or press F12, all the
Lemmings onscreen become bombers with five-second fuses above their
heads. Lemmings will also cease coming out of the hatch if they are
still in the process of doing so. After five seconds, every single
Lemming will blow up in an impressive fireworks display, and you will
be sent to the accountability screen, which tells you how many were
saved and accounted for.
SPECIAL NOTE: The question marks in the field-of-play model represent
the number values that are in those boxes while you are playing.
Now that you know what everything on all those initially befuddling screens
is all about, it's safe to introduce you to the basic concept of Lemmings.
You are given a set amount of Lemmings per level. Out of those many or few
Lemmings, you must save a certain percentage of them. If you're not sure how
many Lemmings encompass the percentage provided, convert the percentage to be
saved to a decimal number (.xx) and multiply the total number of Lemmings by
the decimal number you got.