A shortcode is a WordPress-specific code that lets you do nifty things with very little effort. The main way to invoke a shortcode is to type it into the page or post editor, using square brackets.
[shortcode /] [glossary slug='shortcode' /]
You can also open and close a shortcode, surrounding your text with it to assign the code to that content
[shortcode]my text here[/shortcode] [glossary]shortcode[/glossary]