A slug is an easy to understand text identifier most commonly used in a webpages URL.
When it comes to your stack a slug is automatically assigned when you create your tags.
It will remove capitalisation, special characters and any spaces to make it easier to be understood by our system.
For example if you named your tag Test tag 2014 the slug will automatically be named testtag2014.
The custom slug function is only intended to be used by developers.
For further information please log a support ticket.