A macro is a named snippet of text. They are typically defined with the Pragma: \define:
\define my-macro(parameter:"Default value") This is the macro, and the parameter is $parameter$. \end
<<my-macro>> <<my-macro "The parameter">>
The parameters that are specified in the macro call are substituted for special placeholders within the snippet:
$parameter-name$is replaced with the value of the named parameter
$(variable-name)$is replaced with the value of the named variable).
How Macros Work
Macros are implemented as a special kind of variable. The only thing that distinguishes them from ordinary variables is the way that the parameters are handled.