This article is from the Esperanto FAQ, by Mike Urban firstname.lastname@example.org and Yves Bellefeuille email@example.com with numerous contributions by others.
As with other groups, there are some common acronyms that come up from
time to time here.
PAG: Plena Analiza Gramatiko, an analysis of Esperanto grammar. It is
not authoritative, and many people will disagree with some of
its conclusions, but it is the most detailed reference work to
date on Esperanto grammar.
PIV-S: Plena Ilustrita Vortaro, a very complete Esperanto dictionary
(i.e., it is entirely in Esperanto) containing not only the
officially recognized words, but many more that are in general
(and not so general) use. Some of its entries are dubious, but
it is a highly useful reference work. PIV is now quite
expensive. It was published in 1970, with a supplement in 1987
("PIV-S" means "PIV with Supplement"). A new edition is
currently being prepared.
PMEG: Plena Manlibro de Esperanta Gramatiko, an analysis and
commentary on Esperanto grammar. Available online at
PV: Plena Vortaro. PIV's little brother, so to speak; it was written
in 1953 and contains fewer technical terms, neologisms, etc.
TEJO: Tutmonda Esperantista Junulara Organizo, the World Organization
of Young Esperantists. Members of UEA under 30 years of age are
automatically members of TEJO. TEJO publishes a bi-monthly
magazine called "Kontakto" and a quarterly newsletter called
"TEJO Tutmonde", and sponsors the annual international youth
congress (Internacia Junulara Kongreso, or IJK).
UEA: Universala Esperanto-Asocio, the World Esperanto Association. It
publishes a monthly magazine cleverly titled "Esperanto",
produces a "Jarlibro" (yearbook) containing information on
national and special-interest Esperanto organizations and
contacts, and sponsors the annual international Esperanto
congress (Universala Kongreso, or UK).