Here is a wonderful webcast that provides a very quick, and informative, overview of rapid software testing.
Software testing is when a person is winding around a space searching that space for important information.
James Bach starts by providing a definition of software testing to set the proper thinking for the overview.
Rapid software testing is a set of heuristics [and a set of skills]. Heuristics live at the border of explicit and tacit knowledge... Heuristics solve problems when they are under the control of a skilled human... It takes skill to use the heuristics effectively - to solve the problems of testing. Rapid software testing focuses on the tester... Tacit skills are developed through practice.
Automated software tests are useful but limited. In the context of rapid software testing only a human tester can do software testing (automated checks are defined as "software checking"). See his blog post: Testing and Checking Refined.
Related: People are better at figuring out interesting ideas to test. Generating a highly efficient, maximally varied, minimally repetitive set of tests based on a given set of test inputs is something computer algorithms are more effective at than a person. - Hexawise Lets Software Testers Spend More Time Focused on Important Testing Issues - 3 Strategies to Maximize Effectiveness of Your Tests