What is the difference between class="example" vs. classNames="example" in Ember/handlebars components?

I'm applying a class to a component, and it seems like both of these options work:

Both ultimately result in the rendered HTML having the class, e.g.:

<div class="example-class ember-view">...</div>

Is there a difference between providing the class via class or classNames? Are there any unintended consequences using one over the other?