I'm a physicist and so never had a lecture on algebraic geometry. What I really try to find out for some time now (and it's funny how I don't seem to be able to find it out) is if the modern theory, since the 60's say, is concerned with new objects or if, in the end, they are concerned with objects which where already known before. And here I count an object which comes from gluing together other reasonable objects as not essentially new - I expect all the small parts (this and that ring or module) must have been known before. This question really goes for things with names like K-theory too.
So are schemes and sheaves compilations of things one had before, are they more or less "just" tool for the classification of weird but not totally far fetched spaces (the dimensions seems to be relatively low at least), or are these really new ideas? Is it that people try to understand all the spaces as well as spaces over spaces and so on using new tools, or is it about essentially new things?