I'm having a hard time wrapping my head around opening and reading from a simple text file in Node.js. Part of my problem is that many of the file system functions require a mysterious [mode] argument. This is apparently a four digit number that... does something. I have no idea what and I can't seem to find a good explanation. I suspect that this is something rather basic to elite node.js hackers, but I'm finding it rather mystifying. Can anyone explain what this argument does?