Loosely speaking, a profile is a definition of a set of terms. Ideally, a profile includes both machine-readable information and human-readable information. In HTML 4.01 and XHTML 1.0, a few attributes such as the rel attribute do not have a predefined set of values. Instead, the author can provide values according to need, and then use a profile to explain what the values mean. In our case, we have recommended that authors use the value "icon" and a profile that explains that "when we say icon, we mean 'this is a favicon.'"
In Method 1 above, we use the rel attribute with the link element and choose a profile with the profile attribute on the HEAD element.