A preface is written by the author of the book; a foreword is usually written by someone other than the author.
(Note the difference in spelling between the words ‘foreword’ and ‘forward’, even though they sound similar. ‘Foreword’ literally means ‘words that come before’.)
Both a preface and a foreword describe some of the background to the creation of a book. A preface is usually written by the author of the book, and might describe how the book came to be – or, in the case of later editions, might describe the changes made from the earlier editions. A foreword is usually written by someone other than the author – often someone the author knows, and often someone prominent in the same genre or subject – and might describe some other aspect of how the book came to be, or some relevant aspect of the author’s life.
The exact contents of a preface and a foreword can vary a lot from book to book. They are both optional sections to a book – a book can have both, one or the other, or neither. Many books don’t require either. Importantly, though, both are different to the introduction of the book. If a book has an introduction (not all do), this is the introduction to the subject of the book, not normally talking about how the book itself was written or edited.
The preface and foreword are part of the front matter of a book. They should appear after the table of contents (as both the preface and the forward should be listed within the table).
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