Raku is a language specification similar to C and C++. To actually run programs written in Raku one needs a Raku implementation. There are several implementations varying in their level of maturity and development activity.
Rakudo™ is currently the most actively developed and mature
implementation of the Raku Programming Language. Rakudo can
be downloaded from its website.
There exist other implementations of Raku varying in their level of maturity and development activity. Have a look at the compilers page for an overview.