I believe I gleaned this originally from Jesse James Garrett some time ago and have found it a useful explanation for both myself and others.
Between the two names we have different concerns. Information architecture (IA) is primarily about cognition ? how people process information and construe relationships between different pieces of information. Information design is primarily about perception ? how people translate what they see and hear into knowledge.
Also I consider IA to be far broader in scope to include whole regions of information while ID is concerned with what the people are involved with now.
Both require different skills. Information architects come from a variety of backgrounds, but I sense that a majority of them display an orientation toward language. Information designers, on the other hand, tend to be oriented toward the visual arts. As a result, the majority of information designers come from exactly one discipline: graphic design.
Information architecture belongs to the realm of the abstract, concerning itself more with the structures in the mind than the structures on the page or screen. Information design, however, couldn?t be more concrete, with considerations such as color and shape fundamental to the information designer?s process.
Be mindful that organization and presentation are different concepts. Data can only be organized with in a few principles: Magnitude, Time, Numbers, Alphabet (Chinese by stroke?), Category, Location, and Randomness.
Magnitude, Time, Numbers, and Alphabet are all sequences of some type, which we can use to organize things based on a similar characteristic shared by all the data.
Category and Location are organizations that also use some inherently meaningful aspect of the data around which the data can be orientated.
Randomness is the lack of organization. It is important when we are trying to build an experience that isn?t necessarily easy ? an exploration or game.