Monkey Testing, interesting terminology, but valuable testing in software industry.
Monkey Testing is nothing but random testing of software application or system on the fly, with out the working knowledge of the application. The goal of the monkey testing is to identify any show stoppers or criticals in the software application under test.
Monkey testings are best performed by the automated testing tools. These automated testing tools will be called as 'monkeys' if they work randomly identifying crash or break in the software code.
Monkey testings are inexpensive to perform some basic random testing which will result in finding very few bugs, where as it could be very expensive for load or performance testing, which can result in number of bugs.
Monkey testing can be valuable for software application to identify rather embarrassing show stoppers, but this should not be only testing performed.