CONCEPT

[L:40] Concepts are opposed to intuitions as types of representations. Whereas intuitions have their source in the faculty of sensibility (in receptivity), concepts have theirs in the understanding (in spontaneity, as rules for synthesis).Kant also characterizes the distinction between intuitions and concepts as that between intuitive and discursive cognitions--thus when Kant claims that we have a discursive intellect, he means that we think through concepts (cp. A19/B33). [The objects in question are appearances.
[L:97] Among other distinctions (e.g., higher and lower, wider and narrower), Kant distinguishes pure concepts (which are also a priori concepts) from empirical concepts (which are also a posteriori). Simply put, a pure concept is one which is not "abstracted from" or "drawn from" experience, "but springs from the understanding even as to content". In the Critique, the categories are examples of pure concepts; Kant holds that these concepts, at least, are necessary for experience and knowledge. Empirical concepts "spring from" actual experience, "from which they have been extracted as to their content".

[A43/B61] In the context of the distinction between clear and confused representations, Kant distinguishes "the representation of a body in intuition" from "a concept in the understanding" (exactly why he makes this contrast here is unclear; he denies that appearances are always confused). Despite the apparent confusion in our concept of right (an aggregate of "the subtlest speculation we can develop out of it"), Kant insists that "`right' can never be an appearance; it is a concept in the understanding, and represents a property (the moral property) of actions, which belong to them in themselves".