Template:Void/doc

This template does nothing—more precisely, it throws away its parameters and outputs the null string.

It is useful for programming advanced templates, and is often is used within a template to the right of an equals sign. It may also be used in a template to disambiguate parsing of braces.

It can also be used to temporarily disable code, and unlike "commenting out" with, it nests. This means that  is valid, whereas   will produce.

Alternatives
It's also possible to use, the empty/void/null string for the main namespace.

It can be used in place of  to break character sequence parsing, for example   to force the first closing brace to be treated as part of the template parameter instead of as the end of the template expression.