I'm pretty sure fluct is short for fluctuation. The higher it is, the more variable your ping is: for example, I usually have ping 50, fluct 5, but I'm running on a shared connection, so depending on what other computers are doing, I could be anywhere between 45 and 55 ping (or possibly 47.5 and 52.5, I'm not quite sure how the fluct is measured)
Lag can be a problem for both players involved. I definitely see people jumping around more when I'm lagging, and in a few cases I've ended up with lag so bad that I was basically playing a couple of minutes behind everyone else, targetting ships which end up destroyed before my "target so-and-so" message appears, and taking damage despite having decided that there was too much lag and sitting snugly by the Essex.
However, this is coming from the guy who ended up in a lag sweet-spot where I ended up completely immune to GB missiles. Admittedly the GB I was fighting would often lag past me while I was lining up a SNAC, but it was fun while it lasted.
