title: What's the meaning of 'i' in for loop?
body: <p>In almost every programming language, they use variable <strong>i</strong> when they explain for loop. Like,</p>
  
  <pre><code>for i in 'string':
    print(i)
  </code></pre>
  
  <p>or</p>
  
  <pre><code>for(var i ; i&lt;100 ; i++) {
    console.log(i);
  }
  </code></pre>
  
  <p>etc...</p>
  
  <p>Does it mean anything? Or just a variable with no meaning?</p>
  
  <p>I couldn't find any information about this in google search.</p>