Taken from the Guile homepage:

Guile is a library designed to help programmers create flexible applications. Using Guile in an application allows programmers to write plug-ins, or modules (there are many names, but the concept is essentially the same) and users to use them to have an application fit their needs.

Guile is an interpreter for the Scheme programming language, packaged as a library which can be incorporated into your programs. Your users have full access to the interpreter, so Guile itself can be extended, based on the needs of the user. The result is a scripting language tailored to your application.

CategoryProgrammingLanguages, CategoryFunctionalProgrammingLanguages