Educational theory can refer to either speculative educational thought in general or to a theory of education as something that guides, explains, or describes educational practice.
In terms of speculative thought, its history began with classical Greek philosophers and sophists, and today it is a term for reflective theorizing about pedagogy, andragogy, curriculum, learning, and education policy, organization and leadership. Educational thought is informed by various strands of history, philosophy, sociology, critical theory, and psychology, among other disciplines.
On the other hand, a theory of education can be "normative (or prescriptive) as in philosophy, or descriptive as in science." In the first case, a theory means a postulation about what ought to be. It provides the "goals, norms, and standards for conducting the process of education." In the second case, it means "an hypothesis or set of hypotheses that have been verified by observation and experiment." Whereas a normative educational theory provided by a philosopher might offer goals of education, descriptive "theory provides concrete data that will help realize more effectively the goals suggested by the philosopher." A descriptive theory of education can be thought of as a conceptual scheme that ties together various "otherwise discrete particulars. . .For example, a cultural theory of education shows how the concept of culture can be used to organize and unify the variety of facts about how and what people learn." Likewise, for example, there is the behaviorist theory of education that comes from educational psychology and the functionalist theory of education that comes from sociology of education.
In general, there are currently three main ways in which the term "theory" is used in education:
the obverse of practice--theorizing is thinking and reflecting as opposed to doing;
a generalizing or explanatory model of some kind, e.g., a specific learning theory like constructivism;
a body of knowledge--these may or may not be associated with particular explanatory models. To theorize is to develop these bodies of knowledge.