SRFI is an acronym for Scheme Request For Implementation. The SRFI documents define a lot of syntactic and procedure extensions to standard Scheme as defined in R5RS.
Guile has support for a number of SRFIs. This chapter gives an overview over the available SRFIs and some usage hints. For complete documentation, design rationales and further examples, we advise you to get the relevant SRFI documents from the SRFI home page http://srfi.schemers.org/.