What does the term Penal Servitude mean? Does it mean that you could be let of of prison early?

I have been looking into Victorian court cases and seen phrases such as 'Five Years' Penal Servitude' and so on. If a prisoner was given Penal Servitude, does that mean they were sent to prison and locked up or does it mean they had to do labour outside of jail? And if it was that they were locked away in prison, could they ever have been let out early?