routing/specifying-a-routes-model/"><code>model</code></a> method on Routes,
although they share the same name.</p>
<p>Different apps may have very
different models, depending on what problems they're trying to solve.
For example, a photo sharing application might have a <code>Photo</code>
model to represent a particular photo, and a <code>PhotoAlbum</code> that
represents a group of photos. In contrast, an online shopping app would
probably have different models, like <code>ShoppingCart</code>, <code>Invoi