“First” thus refers to the first printing of a new edition of a book.
TPB refers to a trade paperback edition. Trade paperbacks are ovesized paperback editions.
PBO (Paperback Original) means this ia a first edition first printing paperback, which is also the first time this book was published (the true first edition of this book).
ARC (Advanced Reader Copy) means this was a limited edition paperback (usually paperback) copy of a soon to be released hard back book.
MINI GRADING GUIDE
Books are graded with the ABA standard in mind. That means books range from A (acceptable) to LN (like new) or even N(new).
A full list of typical conditions range from:A, G, VG, VG+, LN, N
Some books may also have the ratings for NF(near fine) and F(fine). The reason for the difference is that some of the venues like Amazon use the like new and new ratings while other venues use the near fine and fine ratings.