From here– ” This term is used to refer to new technologies and what tasks users can possibly perform with technologies at their disposal. The term technological affordance was coined by Ian Hutchby as a reaction against social constructivism.For example, we perceive staircase in terms of what it facilitates – climbing floors – which constitutes its affordance(s). Similarly, Google Plus or Kindle has its own affordances; Kindle is used for reading books and cannot be used the way we use an iPad. Thus, affordances are linked to material-constraints of technologies in question.”
and this is good too–
The word “affordance” is frequently used in writings about new technology. For example, danah boyd has stated that the “affordances” of “networked publics” include things like the persistence of information within them, and the ease by which information can be reproduced and transmitted far beyond its initial context of production.
The simple (but not quite accurate) understanding of the term is that it describes the possible uses that humans can make use of specific technologies. As such, it can sometimes be construed as an example of that great Bugbear of the social studies of technology: technological determinism. Technological determinism is the naive belief that technology is some sort of abstract force which influences society to some degree, but is not itself the product of social forces of any form. Technological determinism comes in several forms – the most common distinction is between “hard” and “soft” determinism, with “softer” versions viewing technology as just one factor shaping society rather than the dominant or only one – but the idea common to all is that technology itself need not be explained as, say, the outcome of competing social pressures, or as influenced by different ideas about what kinds of technologies ought to be developed in what kind of way.