diff --git a/README.md b/README.md
index 64b14ae..647ee99 100644
--- a/README.md
+++ b/README.md
@@ -178,14 +178,16 @@ Point(x=1, y=2)
 
 Iterator
 --------
+**Iterator is any object with next() special method.**
 ```python
-from itertools import count, repeat, cycle, chain, islice
+<iter> = iter(<collection>)                 # Calling `iter(<iter>)` returns the same object.
+<iter> = iter(<function>, to_exclusive)     # Sequence of return values until 'to_exclusive'.
+<el>   = next(<iter> [, default])           # Raises StopIteration or returns 'default' on end.
 ```
 
+### Itertools
 ```python
-<iter> = iter(<collection>)
-<iter> = iter(<function>, to_exclusive)     # Sequence of return values until 'to_exclusive'.
-<el>   = next(<iter> [, default])           # Raises StopIteration or returns 'default' on end.
+from itertools import count, repeat, cycle, chain, islice
 ```
 
 ```python
diff --git a/index.html b/index.html
index e639f46..fddf545 100644
--- a/index.html
+++ b/index.html
@@ -320,12 +320,14 @@ Point(x=<span class="hljs-number">1</span>, y=<span class="hljs-number">2</span>
 (<span class="hljs-string">'x'</span>, <span class="hljs-string">'y'</span>)
 </code></pre>
 <h2 id="iterator"><a href="#iterator" name="iterator">#</a>Iterator</h2>
-<pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> itertools <span class="hljs-keyword">import</span> count, repeat, cycle, chain, islice
-</code></pre>
-<pre><code class="python language-python hljs">&lt;iter&gt; = iter(&lt;collection&gt;)
+<p><strong>Iterator is any object with next() special method.</strong></p>
+<pre><code class="python language-python hljs">&lt;iter&gt; = iter(&lt;collection&gt;)                 <span class="hljs-comment"># Calling `iter(&lt;iter&gt;)` returns the same object.</span>
 &lt;iter&gt; = iter(&lt;function&gt;, to_exclusive)     <span class="hljs-comment"># Sequence of return values until 'to_exclusive'.</span>
 &lt;el&gt;   = next(&lt;iter&gt; [, default])           <span class="hljs-comment"># Raises StopIteration or returns 'default' on end.</span>
 </code></pre>
+<h3 id="itertools">Itertools</h3>
+<pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> itertools <span class="hljs-keyword">import</span> count, repeat, cycle, chain, islice
+</code></pre>
 <pre><code class="python language-python hljs">&lt;iter&gt; = count(start=<span class="hljs-number">0</span>, step=<span class="hljs-number">1</span>)             <span class="hljs-comment"># Returns incremented value endlessly.</span>
 &lt;iter&gt; = repeat(&lt;el&gt; [, times])             <span class="hljs-comment"># Returns element endlessly or 'times' times.</span>
 &lt;iter&gt; = cycle(&lt;collection&gt;)                <span class="hljs-comment"># Repeats the sequence indefinitely.</span>