trading activity volumes- what gives?

Hi, a couple of questions from a novice.

From these "Conditions" of trades below,
CX
CXXT
EQ
ET XT
L3 XT
L4 XT
L5 XT
NXXT
OS XT
S1 XT
SX XT
XT

1) Is there a good explanation of what they are, and who would use them for what purpose?

2) How do you tell the Short-sellers from the code?, or are those of you referring to shorts using another source?

3) Finally, here is my analysis of the volume of trades for about a month for ILU.
Volume Bin--------Frequency---------Cumulative %
5 ---------- 18979 ---------- 12.65%
10 ---------- 8579 ---------- 18.37%
50 ---------- 28354 ---------- 37.28%
100 ---------- 17997 ---------- 49.27%
200 ---------- 21515 ---------- 63.62%
400 ---------- 21597 ---------- 78.02%
800 ---------- 17527 ---------- 89.70%
1600 ---------- 10068 ---------- 96.41%
3200 ---------- 3781 ---------- 98.93%
6400 ---------- 1148 ---------- 99.70%
12800 ---------- 312 ---------- 99.91%
25600 ---------- 96 ---------- 99.97%
51200 ---------- 35 ---------- 99.99%
102400 ---------- 3 ---------- 100.00%
204800 ---------- 1 ---------- 100.00%


Who, how and why can people do trades of 1 or two shares, which is way below a marketable parcel?

Appreciate thoughtful responses.