Please read page 1 of this thread for more detail.
here is the post by the founder of these thread Mr ormania
1) Visa Bulletin (VB)
Visa Bulletin is a publication regarding
immigration to the United States published by the
United States Department of State. The primary
purpose of this bulletin is to provide an updated
waiting list (also known as Priority Date) for
immigrants that are subject to the quota
system.The content of the bulletin is available on
the web address
http://travel.state.gov/content/
visas/english/law-and-policy/bulletin.html
2) Current
We say current when visa numbers are available
for a specific qualified applicant. Visa numbers are
available only for applicants whose priority date is
earlier than the cut-off date listed in the tables
3) 1st NL and 2nd NL
First NL (1st NL) is the First Notification Letter that
you received explaining that you are a winner.
While the Second NL (2nd NL) is the Second
Notification Letter that the Kentucky Consular
Center send to your email describing your date,
time and place of interview.
4) C.O
Is the Consular Officer who will conduct your
interview in the embassy when you go for the
interview.
5) P.O.E
Is the Port of Entry. It is the first entry point where
you enter the United States of America after your
entry is approved by the US Immigration officers.
CHEERS!