A life sentence can be life in prison or it can also mean life with parole in 25 years.
The life sentence depends on how the person was sentenced to prison in court.
If a person is sentenced to life without parole then the person will serve the rest of their life in prison and never get out of prison unless they are dead.
If a person is sentenced to life with parole then the person can be eligible for parole after serving at least 25 years.
It does not mean the person will get released from prison after 25 years although there's a small chance they could be.
The person has to go up against a parole board and the parole board makes a decision on whether or not to let the person be paroled.
People sentenced to life with parole rarely get out on parole.
So even if a person is sentenced to life with parole they should expect to remain in prison for the rest of their lives.
Life without parole you should certainly expect to live in prison the rest of your life because that is what it means.