HTML attributes: item*

An HTML element can be annotated with the (boolean) attribute itemscope which indicates that the content of this element and its child elements is about a particular item:

<div itemscope …>
  …
</div>

itemscope by itself is rather meaningles because it does not specify what the conent is about. Therefore, itemscope must be combined with either itemtype or itemref:

<div itemscope itemtype="https://schema.org/Person">
  …
</div>

The value of itemtype defines a vocabulary about that type. Such a vocabulary basically consists of key-value pairs. The value of the child element's itemprop attribute corresponds to a key, the content of the child element to the value:

<div itemscope itemtype="https://schema.org/Person">
  <span itemprop="name">John Doe</span>
  …
</div>

<div itemscope itemtype="https://schema.org/Person">
  <span itemprop="name">John Doe</span>
  <span itemprop="composer" itemtype itemtype="https://schema.org/MusicComposition">Programming and Fugue in C-Sharp</span>
  …
</div>

<div itemscope itemtype="https://schema.org/Person">
  <a href="John-Doe.html" itemprop="url">John Doe</span>
</div>

<div itemscope itemtype="https://schema.org/Person">
  <span itemprop="name">John Doe</span>
  <link href="John-Doe.html" itemprop="url" />
  was a mythical …
</div>

<div itemscope itemtype="https://schema.org/Person">
  <span itemprop="name">John Doe</span>
  <meta itemprop="relatedTo" content="…" />
  was a mythical …
</div>