Well, to start, there's no book part called a "Forward." It's a "foreword."
And it should probably come first if it's written by someone else.

Front matter usually begins with an outsider's promotion of the book,
whether it's called a preface, an introduction, or a foreword.

The author himself can include both a preface (or foreword--they're the same
thing) and an introduction. The preface usually explains why the author
decided to write the book or gives other personal background information,
and it often includes the acknowledgments, though they can also be a
separate part. In any case, the preface/foreword is a personal thing, not
directly related to the topic of the book.

The introduction is usually an introduction to the subject of the book. It
may give background information on the subject or briefly review the
literature in the field.

I'm not sure what a prologue would be in a nonfiction book. In fiction it
usually presents events that occurred long before the beginning of the main
story. Sometimes the relationship of these events to the plot of the book is
not apparent until well into the story. Similarly, an epilogue tells how
things ultimately turned out, many years after the conclusion of the main
story.