title: What is the `it` in Kotlin lambda body?
body: <p>For example in these two following codes:</p>
  
  <pre><code>File("./file1.txt").forEachLine { println(it) }
  </code></pre>
  
  <p>and</p>
  
  <pre><code>File("somefile.txt").bufferedWriter().use { out -&gt;
      history.forEach {
          out.write("${it.key}, ${it.value}\n")
      }
  }
  </code></pre>
  
  <p>In this code what does <code>it</code> mean?</p>