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Life In Prison from WikiPedia:

Life imprisonment (also known as a life sentence or life incarceration) is a sentence of imprisonment for a serious felony crime (e.g., first degree or serial murder - especially if aggravating factors are present - and other such crimes like aggravated rape and other cases of predatory sexual assault, severe or violent cases of drug or human trafficking and dealing, arson resulting in death or great bodily harm, certain terrorism and hijacking cases, high treason or espionage, chronic drunk driving where death has occurred, aggravated cases of burglary or bank robbery or armed robbery resulting in death or great bodily harm, etc.), where the convicted person is to remain in prison for the rest of his or her life.

However, in many jurisdictions there are formal mechanisms to request parole after a certain time. This means that the convict could be entitled to spend the rest of the sentence (i.e., until they die) outside prison; this is usually conditional depending on conduct and with certain restrictions or obligations. In contrast, in jurisdictions without life imprisonment, a convict after having served the given prison sentence is free upon release.

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