that particular pairing sounds like the result of a long, and perhaps forgotten, intermingling of various discourses (something from the visual arts, something from early psychology, something from urbanism). In the simplest terms, its describing something that either pops out from the background/context/fabric or something which blends into or seamlessly makes up or participates in the background/context/fabric. one is a little more 'shaped', the other not.

there's probably a good number of directions this could be pulled into, but that's the basics.

yes, the extreme epistemology of the former would probably be that of how we conceive of architecture as objects; you will hear people speak of buildings as objects (that stand out, in their object-hoodness)

and  of the later would be that of how we conceive of architecture within the guise -or as an extension- of landscape (be it urban or natural). As boy in the well says, this architecture is read within the surrounding-scape.

Its an interesting polarity. In a way its about how a buildings finishes itself off in relation to the outside. To what degree it mimics some aspect of the surrounding and/or to what degree it is hermetic. But it also need not be about mimicry.

For instance, is Le Corbusier's Venice hospital design a fabric or an object? It can really be viewed as both. As a mat-building, its spatial agglomeration approximates the fabric - whereas, viewed from outside (or, to be more specific, with a hermetic-prejudiced viewpoint) it is seen as somewhat of a compound-object architecture.

In a way, while the difference might be convenient - epistemologically and taxonomically - even useful as a design tool, it is good to also keep in mind that the conception of this difference is also conditioned by inconsistently-biased tendencies.

or...what boy in a well said above.