title: Use of underscore in variable and method names
body: <p>I got confused with the (<em><a href="https://en.wikipedia.org/wiki/Naming_convention_(programming)" rel="nofollow noreferrer">naming convention</a></em>) use of underscore <code>_</code> in variable names and method names as their starting letter. For example, <code>_sampleVariable</code> and <code>_getUserContext()</code>. When should I use it?</p>