-This is the GNU parser generator which is mostly compatible with yacc. Many
-programs use this as part of their build process. Bison is only needed on
-systems that are used for development.
+Bison is a general purpose parser generator which converts a grammar
+description for an LALR context-free grammar into a C program to parse
+that grammar. Bison can be used to develop a wide range of language
+parsers, from ones used in simple desk calculators to complex
+programming languages. Bison is upwardly compatible with Yacc, so any
+correctly written Yacc grammar should work with Bison without any
+changes. If you know Yacc, you shouldn't have any trouble using Bison
+(but you do need to be very proficient in C programming to be able to
+use Bison). Many programs use Bison as part of their build process.
+Bison is only needed on systems that are used for development.