What is the difference between an instruction to the jury regarding a death sentence and a sentence of life without parole?

claim that the trial court erred by giving, at the defendant's request, an instruction providing:" 'If you find that a verdict of death is appropriate, you must assume that such penalty will be imposed, ' without giving a similar instruction regarding a sentence of life without the possibility of parole." We concluded the trial court did not err in so instructing the jury regarding a death verdict, because although "it would be erroneous to instruct the jury that if it returns a death verdict, the sentence of death will inexorably be carried out[,] the trial court may give such an instruction at the defendant's request." (Cox, supra, 30 Cal.4th at p. 967; see also People v. Williams (2008) 43 Cal.4th 584, 647 [observing that "to instruct the jury that it must assume that a sentence of life without the possibility of parole means the defendant will be imprisoned for the rest of his or her life is inaccurate because it fails to acknowledge that the Governor retains the power of commutation"].)