Definitions for "Functional Testing"
the system testing of an integrated, blackbox system against its operational (i.e., functional) requirements.
Quality assurance that a web site performs properly. All aspects of the user interface, navigation between pages and off-site, multilingual navigation, etc. are tested. Testing is required in all the current browsers and on the major operating systems and platforms.
Testing whether a computer program does the things it's supposed to. This testing assumes that the original specifications were correct.