Go to 'Product > Product Attributes'. A list of all current attributes appears. You can click to create a new attribute, or edit an existing one.

Attribute type is fixed as 'text', but other types may be supported in future.

You can control if the attribute is displayed in the product page from the checkbox – unchecking the box means the attribute is hidden from displaying there.

If all the attributes of a product are hidden in this way, the 'product details' section on the product page will be hidden.

You can control whether an attribute is searchable too, with the 'include in search' checkbox. For example, you might not want voltage to be searchable, but you would most likely want the author attribute for a book to be searchable, or the ISBN number, as customers are very likely to use these to find particular items.

The final option is 'Show on comparison table'. This sets the circumstances under which the attribute will be displayed when comparing products.