A basic definition of "first edition"

 Often, you will find that book shopperrs concentrate their efforts only on first editions of their topic of interest.  A first editions is more desireable to the collector than later printings of the same book.

... first edition means the first printing of a book. Edition and printing can be used fairly interchangeably in talking about collectible books, especially in regard to modern fiction.

 {https://www.biblio.com/book-collecting/basics/how-to-identify-first-editions/)