Different Meanings To A Life Sentence??

Hello, this is my first time posting in a forum and I have a question. Are There Different Meanings When Someone Is Sentenced To Life? The Judge In A Case Of My Relative Said For Him To Take A Sentence Of 15 years To Life. I Was Just Wondering How Long Would He Have To Be In Jail Until He Can Get Out Or Have Parole Or Whatever.I'm Sorry If This Doesn't Make The Best Of Sense, I'm Trying My Best To Try And Explain My Question. Thank You!