Yes life in prison sentences do in most cases mean that the person will remain in the prison for the rest of their lives.
That means that when the person is sentenced to life in prison without parole the person will not be able to leave prison.
The person with life without parole will stay in prison until they die and will only be leaving the prison in a body bag and dead.
However there's also another life in prison sentence that is life in prison with parole at 25 years.
That means that the person has to serve at least 25 years of their lives in prison before they can come up for parole and see the parole board.
That does not mean the person will get out of prison after 25 years.
But there's a chance that the person may get out of prison at 25 years but even life with parole prison sentences can mean the person remains in prison for the rest of their lives.