In the field of computer science, what is an algorithm?

An algorithm, in its most basic form, is a mathematical procedure for solving a problem in a finite number of steps. An algorithm is a set of instructions that describes not only what has to be done but also how it should be done in the realm of computers. A programmer or computer scientist can use algorithms to direct his machine to query database A for last month's sales figures, compare them to the previous month and the same month last year, and display the results in a bar graph.