This is a very minor point, but one which had been grating me for a while. I apologize for asking a relatively trivial question, but nevertheless hope that it is suitable for MO since it should have a definite answer.

In Mumford's books, for instance Curves on Surfaces or Red Book, there is a thing called "prescheme" which looks like a scheme, and scheme is something else.

But this terminology does not seem to be used elsewhere, and if at all is the case, prescheme seems to be something cruder than scheme.

I will be grateful for clarifications regarding this terminology. "Curves on surfaces" is a nice book, but whenever I pick it up I find myself wondering about this without any avail.

Edit: What does Demazure and Gabriel say about this? I do not know enough French to look it up myself.