An anthology may begin with an idea, and slowly build up, picking up a bit of this, and some of that, until all of the bits and pieces merge together into some kind of meaning, at least in the eye of the editor of that anthology.
And an anthology, like any other book, has things it needs to have, to become a book, a saleable item, one that can be found in libraries, and book shops. There are expected things, necessary things, useful things, and just to pique the interest of reviewers and readers, surprising things.

The necessary things are items such as written words, poetry or prose, from a range of writers who had something they wanted to say, and perhaps answered the call for submissions for the anthology, and had their work accepted by the editor. These are the ‘guts’ of the book, the meat that will make the anthology something spending the necessary time on, to read it all.
But there are other things the book will need, that the reader doesn’t really need to know about, but the editor does, if they want to make the book a thing that will fit into the places where the reader may find it. A book needs an ISBN, and a barcode, to better enable librarians and book sellers to deal with that book. And inside of the book, as well as the pieces written in response to a request for them, needs to be list of contents, and those contents might also be a foreword, and an introduction, and then those so important contents.
After the contents, there may be a list of the contributors, containing a few words about each of them and perhaps with details about how to read more about them, such as a link to their own website, it they have one, as well a list of their books or articles written.
And so an idea becomes a thing, a book, to be printed, and then maybe launched, shared, anyway, marketed, so copies may be purchased or borrowed, and the editor smiles, glad to see idea become reality. And then waits for the next idea, and the new bits and pieces …