Update readme

README.md

@@ -8,8 +8,7 @@ made with POSIX Shell.
     COMPILE_R7RS=${SCHEME} compile-r7rs -o main -I libs -A other_libs main.scm
     ./main
 
-
-## Implementations
+## Suppoerted implementations
 - capyscheme
 - chezscheme
 - chibi
@@ -33,5 +32,11 @@ made with POSIX Shell.
 - tr7
 - ypsilon
 
+## How it works
+
+With compilers, it compiles. With interpretes it creates a script file which
+contains shebang to run the implementation with given -I and -A paths and
+contents of input file (.sps or .scm).
+
 ## Misc
 - No support for -D yet.