Confusion over various webpack shimming approaches

I'm a little confused on the various ways webpack allows to expose a variable that isn't available on npm or to be put in the bundle. I was able to expose the google visualizations chart script's global google var by using

resolve: {
    extensions: ['.js', '.json'],
    alias: {
      'google': path.resolve(__dirname, 'vendor', 'google.js')
    }
  }

combined with

  plugins: [
    new webpack.ProvidePlugin({
      'google': 'google'
    })
  ]

however looking at the webpack docs there a couple other ways to shim, which look like they might do something similar. There is imports-loader and exports-loader, and script-loader. I know that I've linked to the docs, but I still find their descriptions of when these four should be used a bit unclear.

Also looking at this example, is this require not assigned to a variable? Where is it meant to go? And where is the documentation on what is going on with this syntax?

require("imports?$=jquery!./file.js")

Can someone provide me some examples of when each of these should be used?

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