Guile is an implementation of the Scheme programming language. Scheme (and Lisps in general) are well suited for writing Domain Specific Languages. Guile ishomoiconic. It has a powerful object-oriented programming framework and it is optimised for immutability
Guile has no Global Interpreter Lock.
Guile doesn't have a particular overhead for calling functions which makes it possibly as fast as C.
Guile has pre-release of a new JIT with instant startup from native code caches.