The Concept of Structure
The concept of "structure" is a complex one and I don't intend, for the moment, to explore its many depths and facets in great detail. One way of thinking about the concept, however, is to see it as a framework of rules and relationships, in the sense that all relationships are governed in some way by rules of behaviour.
In the social world, for example, these rules relate to the behaviour of people, whereas in the natural world these rules might relate to things like the relationship between atoms.
A relatively simple way of visualising the concept of structure is to use a familiar analogy, that of the grammatical structure of language. "Grammar", in this respect, specifies the rules on which the relationship between letters and words are based.
For example, a sentence has, by definition, a certain structure; it always has a subject , a verb and an object. When individual words are joined to create a sentence they take-on a different meaning (and their meaning changes to reflect their different arrangement within sentences).
For example, the sentence "Call me tomorrow at 7pm" has a different meaning to the same words arranged in a different way ("7pm me at call tomorrow", for example), although English grammar is sufficiently flexible to allow the sentence "At 7pm call me tomorrow". The sentence "At 7pm me call tomorrow", while understandable, has a different meaning to the first sentence we constructed...
Although this is starting to become complicated, it does indicate how we can think about the "structure of a society". In this instance, the "rules" that govern relationships are things like values (general guidelines for our behaviour) and norms (specific behavioural guidelines in particular situations).
Finally, although social structures are, by definition, relatively permanent features of the social world (you could think, for example, about "family structures" or "work structures"), it is important not to see them as "things" - they do not exist outside the people who create them (just like a language that is not used by anyone effectively ceases to exist).
They do, however, have the appearance of a force, acting on our behaviour. This is because they carry with them certain expectations and imperatives; if, for example, you are speaking "English" your speech is expected, by others, to conform to certain rules. Similarly, if you are living in a particular society you are expected to conform to certain norms.
It is in this sense of expectation over how people should behave in certain situations that we can locate the essence of the concept of structure; it represents, in basic terms, a framework of rules and relationships into which we, as individuals, are expected to fit.