What the usage of tryHandle and handle

Hello all,

What the usage of tryHandle and handle is?

And, when I should use it?

// Somebody wants our the selection
long FXWindow::onSelectionRequest(FXObject*,FXSelector,void* ptr){
  return target && target->tryHandle(this,FXSEL(SEL_SELECTION_REQUEST,message),ptr);
  }

  // Update Alpha text fields
long FXColorSelector::onUpdAlphaText(FXObject* sender,FXSelector,void*){
  FXString value;
  if(isOpaqueOnly()){
    sender->handle(this,FXSEL(SEL_COMMAND,ID_HIDE),NULL);
    }
  else{
    ...
    }
  return 1;
  }


Thank you
-Feng