Structuralism was a philosophical movement which achieved its heyday in the 1960s. Styles of thought characterized as structuralist were notable for the fact that they adopted linguistics in the form developed by the Swiss linguist Ferdinand de Saussure who died in 1913 as a methodological model, and applied it to a very diverse range of disciplines. Much has been made of Foucault's protests that he was not a structuralist, but up until the late 1960s, he was quite willing to identify himself with the movement. There is no doubt that Foucault was, and in fact, always remained, closely aligned to the structuralist movement, if we define 'structuralism' as a movement focused on the examination of the relations between things and their structures at every level of culture and knowledge, as opposed to attempts to describe things in their essence. Structuralism also rejected the whole notion of an unchanging and universal human subject or human nature as being at the centre and origin of all action, history, existence and meaning. But where Foucault parted company with the structuralists, and one of the major reasons for his insistence that he was not associated with the movement, was his rejection of the ahistorical formalism often adopted by those espousing structuralist method. (From michel-foucault.com)
Structuralism found popularity in France in the 60s, replacing existentialism in the philosophical limelight of the time. Its followers were seen as quite rigid and antihumanitarian, in direct opposition to Sartrian thought. Structurualists challenged the existentialist view that an individual has the power to determine his destiny with the idea that he has no control over the cultural forces that work together to determine who he will become. These structures, while they might not be changed, can be understood by looking at the broader picture (4).
The belief was that phenomena could be explained with "mental models" that could be based in reality (1). The reality, however, is not physical or found in nature as a Marxist might suggest, but rather only in one's mind as social or cultural realities. Most structuralists define two levels of thought - the surface structure and the deep structure, the former being related to the consciousness, and the latter to unconsciousness. An understanding of both and how they influenced one another was essential.
Structuralists feel that human mental processes are based on a similar structure of binary opposition, regardless of culture. Such oppositions might include "hot/cold" or "male/female", and are the underlying principles of many cultural practices or beliefs. Unpacking the hidden realities beneath such cultural expressions might suggest how individual cultural elements might be best explained within a broader system of underlying truths (3)
(1) http://www.utpa.edu/faculty/mglazer/Theory/structuralism.htm (2) Lett, J (1987) The Human Enterprise. Boulder CO: Westview Press, Inc. (3) http://www.as.ua.edu/ant/Faculty/murphy/struct.htm (4) http://www.philosopher.org.uk/poststr.htm