Webpack plugins definePlugin and CommonsPlugin
<p>Im pretty new to webpack (and process managers).  Is it possible for someone to please help me and explain these two plugins as I am not finding any documentation on them any where.  What they doing??? Whats their purpose???</p>

<pre><code>var definePlugin = new webpack.DefinePlugin({
    __DEV__: JSON.stringify(JSON.parse(process.env.BUILD_DEV || 'true')),
    __PRERELEASE__: JSON.stringify(JSON.parse(process.env.BUILD_PRERELEASE || 'false'))
 });

 var commonsPlugin = new webpack.optimize.CommonsChunkPlugin('common.js');
</code></pre>