Unlike many other errors, this exception is not generated by the Maven core itself but by a plugin. As a rule of thumb, plugins use this error to signal a problem in their configuration or the information they retrieved from the POM.
The concrete meaning of the exception depends on the plugin so please have a look at its documentation. The documentation for many common Maven plugins can be reached via our plugin index.
For the special case of a network-related problem during artifact download or upload, you can also consult the following articles: