"A run time environment"
Node allows us to run javascript on OS instead of browser We need a server to create a website or webapp
###Server A program running on a computer somewhere that can communicate with clients
##Modules moduel.exports = exports specific parts of a program A "require" of the file will return this
##Require Find(with path (. or ./) or assumes its in ./node_modules), execute and import the files
fileB var x = 'foobars'; module.exports = x;
FileA var y = require('./fileB'); console.log(y) // foobars
##npm (node package manager) Command line tool that finds libraries and downloads them, and keeps a list of dependencies in package.json
- kick off some external process
- register and event handler that happens when it's done (Callback)