I'll include a bit of the intro to let folks know what they're getting into

Dialectical materialism is the world outlook of the Marxist-Leninist party. It is called dialectical materialism because its approach to the phenomena of nature, its method of studying and apprehending them, is dialectical, while its interpretation of the phenomena of nature, its conception of these phenomena, its theory, is materialistic.

Historical materialism is the extension of the principles of dialectical materialism to the study of social life, an application of the principles of dialectical materialism to the phenomena of the life of society, to the study of society and of its history.

When describing their dialectical method, Marx and Engels usually refer to Hegel as the philosopher who formulated the main features of dialectics. This, however, does not mean that the dialectics of Marx and Engels is identical with the dialectics of Hegel. As a matter of fact, Marx and Engels took from the Hegelian dialectics only its "rational kernel," casting aside its Hegelian idealistic shell, and developed dialectics further so as to lend it a modern scientific form.

"My dialectic method," says Marx, "is not only different from the Hegelian, but is its direct opposite. To Hegel, ... the process of thinking which, under the name of 'the Idea,' he even transforms into an independent subject, is the demiurgos (creator) of the real world, and the real world is only the external, phenomenal form of 'the Idea.' With me, on the contrary, the ideal is nothing else than the material world reflected by the human mind and translated into forms of thought." (Marx, Afterword to the Second German Edition of Volume I of Capital.)

When describing their materialism, Marx and Engels usually refer to Feuerbach as the philosopher who restored materialism to its rights. This, however, does not mean that the materialism of Marx and Engels is identical with Feuerbach's materialism. As a matter of fact, Marx and Engels took from Feuerbach's materialism its "inner kernel," developed it into a scientific-philosophical theory of materialism and cast aside its idealistic and religious-ethical encumbrances. We know that Feuerbach, although he was fundamentally a materialist, objected to the name materialism. Engels more than once declared that "in spite of" the materialist "foundation," Feuerbach "remained... bound by the traditional idealist fetters," and that "the real idealism of Feuerbach becomes evident as soon as we come to his philosophy of religion and ethics." (Marx and Engels, Vol. XIV, pp. 652-54.)

Dialectics comes from the Greek dialego, to discourse, to debate. In ancient times dialectics was the art of arriving at the truth by disclosing the contradictions in the argument of an opponent and overcoming these contradictions. There were philosophers in ancient times who believed that the disclosure of contradictions in thought and the clash of opposite opinions was the best method of arriving at the truth. This dialectical method of thought, later extended to the phenomena of nature, developed into the dialectical method of apprehending nature, which regards the phenomena of nature as being in constant movement and undergoing constant change, and the development of nature as the result of the development of the contradictions in nature, as the result of the interaction of opposed forces in nature.

In its essence, dialectics is the direct opposite of metaphysics. <note from Alaska, skoubalon on death watch since he's a metaphysics nerd>