title: What is the name of the "[ ]" functionality that can be added to a wordpress blog or page?
body: <p>Please feel free to format the question title. </p>
  
  <p>I have been coding a few plugins, and I want a plugin that I can call directly from a page or blog post. </p>
  
  <p>I have seen lots of plugins implement a "[]" on the page/blog editor and I am trying to replicate that behavior. </p>
  
  <p>For example: I want the functionality to write a blogpost, and call this function that echos "Hello world!". </p>
  
  <hr>
  
  <pre><code>Hello this is a page. [hello]
  </code></pre>
  
  <hr>
  
  <p>And the output would be:</p>
  
  <hr>
  
  <p>Hello this is a page. Hello world!</p>
  
  <hr>
  
  <p>What is this functionality called and if I could get an example on how to code it?</p>
  
  <p>Thanks!</p>