[racket] How to read procedure documentation?

Hi there,
I don't seem to know how to read procedure documentation like in the
following example.

    (file->string path [#:mode mode-flag]) → string?

  path : path-string?
  mode-flag : (or/c 'binary 'text) = 'binary


I would expect that the first parameter path is a string and that the
second parameter is an optional parameter denoting a file mode. Further
I would assume that file->string returns a string containing the whole
file.