class - model.frame, UseMethod, and R bytecode reference -- what is this? -

General reference: I am trying to find the code that determines model R. logic and later Call one of model.frame methods.

When I run "model.frame" to reveal my R source code, I get the following:

  & gt; Model.frame function (formula, ...) UseMethod ("model.frame") & lt; Bytecode: 0x21a04c8 & gt; & Lt; Environment: Namespace: Statistics & gt;   
 Specific question: "Bytecode: 0x21a04c8" What is it saying? Is this potentially useful in my context?   
 
 
 Uses the  methods (model.frame)  to detect methods Please. In general, you will use  model.frame.default  almost all the time.