An RSF [Component] (e.g. {{UIInput}}, {{UILink}}) is said to __''peer''__ with a tag in the markup which shares the same {{[rsf:id|IDs]}}. For example a component produced like 

{{{
  UIInput.make(form, "category-name", "#{category.name}");
}}}

could peer with a tag in the markup written like 
{{{
<input rsf:id="category-name" size="30" type="text" value="Snacks" /> 
}}}

The term "peering" is taken from the good old days of Sun's [AWT|http://java.sun.com/products/jdk/awt/] windowing toolkit for Java, where operating-system-side native components were said to "peer with" Java-side representations such as {{java.awt.Button}}. The "pairing up" of a Java-side RSF primitive component together with a "native-side" markup tag by RSF's [IKAT] renderer is conceptually very similar.

Sun has considered AWT at EOL as of 1999, but you can't keep a good idea down. Eclipse's [SWT|http://www.eclipse.org/swt/], much more performant and usable than Sun's [Swing|http://en.wikipedia.org/wiki/Swing_(Java)] makes use of native components once again in a "peering" type arrangment, although with a much better division of labour than in AWT. An analogy that has sometimes been made is that RSF's relation to JSF is comparable to AWT's relation to Swing.