It took me a couple tries to parse the headline. Usually, 'C compiler' means 'a compiler that compiles C (to something else)', whereas here it means 'a compiler that compiles to C (from something else)', in this case Scheme.
Chicken compiles Scheme to efficient C that is then compiled to machine code by your machine's existing C compiler.
Chicken compiles Scheme to efficient C that is then compiled to machine code by your machine's existing C compiler.