Somewhat broad category of mathematical subjects that concern discrete, rather than continuous objects. A good example of this distinction is the kind of functions you study in discrete math. Where as calculus differentiates and integrates functions defined for every value in some interval of real numbers, the kind of function examined in discrete math is often called a 'mapping', a rule that associates each members in one set with one in another. Often, these sets are finite, and so the elements are discrete, rather than continuous.
The topics addressed in a discrete math class vary, but it seems every curriculum has mathematical logic, set theory, formal proof techniques,
number theory and probability. Other topics you might run into are
abstract algebra (e.g.,
group theory),
graph theory, linear programming, game theory and algorithmic complexity.
In addition to teaching students very important methods of proof and logic, discrete mathematics also gives a fun rundown of topics with a lot of practical applications.
(In the US, the median income of the few people who have the attention span and maturity to learn about things like discrete math is $81,240. True fact.)
Example:
The previous contributor knocked discrete math on the Internet, not realizing that his message was
routed to this server with an
algorithm based on
graph theory, which is a part of discrete math. Jesus fucken' Christ-on-a-cracker, is he ever dumb.