Learning theories make general statements about how people learn (at least for a given class of learning types). Therefore learning theories are mostly descriptive.
As an example, situated learning claims that learning is strongly tied to the context and the activity in which it occurs. In order to learn a concept in a useful way it must be learned in the culture in which is has been developed and is used. Activity and perception are prior to conceptualization. The teaching and learning situation is characterized as cognitive apprenticeship. From that follows that the acitvity of learning must take place in an authentic situation.
Learning theories also can be prescriptive (tell how people should learn), but prescription is rather the role of pedagogical theory. DSchneider believes that it mostly a bad idea to blend learning and teaching theory. E.g. if one believes that knowledge is constructed one does not necessarily have to adopt a "constructivist" instructional design model. Different teaching strategies may have to combined.
In any case, learning theories play explicitly or implicitly a major role in instructional design models and the educational technology field. Conversely, we may argue that no instructional model and no technology is "innocent". They all view learning in certain way, i.e. from a very practical point of view they put constraints on what kinds of learning they support.
In the literature related to education (in particular in educational technology, it is not always easy to separate learning theory from educational theory.
Most introductory texts distinguish between three large families of thought.
The difference between behaviorist views and cognitivist views is that cognitivism makes explicit assumptions on how we store and manipulate informations and that education should be concerned by analyzing and influencing thought processes. The difference beween cognitivism and constructivism is that cognitivists like behaviorists are "objectivists", knowledge and tasks to be learned can be identified and performance can be measured. Constructivists, on the other hand believe that both learning and teaching is a more open-ended process.
(very shortly for the moment)
Gerry Stahl (2003: 6) provideded a graphical representation of how philosophical influences led various theories of leaning, in particular social versus individual theories. On the right hand side of the picture is a list of learning theories.
Note: DSchneider would not qualify activity theory as a learning theory, but rather as a framework to analyse social behavior.
DSchneider argues that many components (or rather sub-theories) of learning theory are relevant: