import Patrick Michaud's suggested answer as-is

doc/Language/faq.pod

@@ -479,6 +479,25 @@ string|/type/Match>.
 
 C<OpaquePointer> is deprecated and has been replaced with C<Pointer>.
 
+=head1 Implementation Details
+
+=head2 What language is Rakudo written in?
+
+The glib answer is that Rakudo is written almost entirely in Perl 6, with a
+small bit of C or Java glue code thrown in depending on what virtual machine
+backend Rakudo is being compiled to use (e.g., MoarVM or JVM). If you look at
+the files in the "src/" directory in the Rakudo repository, you'll see that
+just about all of them are Perl 6 source code files
+
+The more detailed answer is that Rakudo is written in a mixture of Perl 6 and
+NQP ("Not Quite Perl"). NQP is a lightweight Perl 6-like environment for
+virtual machines; it's designed to be a high-level way create compilers and
+libraries for virtual machines (such as MoarVM and JVM) using Perl 6 syntax. So
+then the question naturally becomes "What language is NQP written in?", and the
+answer is that NQP is a mixture of (1) NQP code, (2) whatever language the
+underlying virtual machine is using, (3) some third-party C and Java libraries,
+and (4) some bootstrapping files created by earlier runs of the build process.
+
 =head1 Meta Questions and Advocacy
 
 =head2 When will Perl 6 be ready? Is it ready now?