What is a 1st edition?
Basically it is a book that the publisher has released, either on the day the book is launched, or when there is going to be a limited numbered amount of copies with "This is one of 500 or 300 books" as an example.
The latter was done for the first Harry Potter book and most of those got published down under, so to be found elsewhere would be pretty rare and now these 500 books are - if in "fine" condition worth a lot of money.
There are several clues to help you identify a first:
Copywrite date will match printing copy date.
The publisher may print on the Colophon page " Book 1st printed /issued on 21st Sept 1998 " They will usually also add which country was truly first.
There may be a number line going down 10 9 8 7 6 5 4 3 2 1 or 9 0 8 7 6 5 4 3 2 1.
The publisher may print the printing date on the title page under their company name
However, it becomes a might harder for Antiquarian books that are over 100 years old. I use various research engines to find out if there is any info held on the book that I have and if I cannot find anything at all, then I put that it may be a first edition. There will always be somebody who may know different.
Condition: Why it's important to describe a book accurately.
Mint = Brand new & unread.
Fine = Crisp clean Jacket & book that has been read once
Very good similar to fine with edge rubbing to Jacket or book.
Good = Jacket has minor damage but is 99% complete and light foxing.
Fair = Light foxing with well chipped Jacket.
Poor = Jacket either missing or badly damaged and book falling apart.
The above conditions are often seen in listings as: F/F or VG/G all this means to the layman is Book has a Very good book in a Good jacket. If it just states VG or G then there will be no jacket or it will be a paperback softcover.
Foxing is a fungus that attacks older books or those that have been badly stored. Chloromine T can reduce this problem by killing off the fungus.
F/end paper = literally first blank page to book - library tickets usually stuck on them if ex - lib.
Colophon = page where publishers details & printing date/edition info located.
Finally ! BCA or book club editions are not genuine 1st editions and should be treated as reading copies only. They never have an ISBN on back of jacket and usually state that they are book editions printed with Original publishers permission.