What is meant by "Sharia" in the definition of the Messenger as "he to whom a new Sharia was revealed," and does it mean a book or what?

What is meant by "Shar" (Divine Law) here is the new legislation that did not exist previously, as Allah the Almighty said concerning Jesus (peace be upon him): "And [I have come] confirming what was before me of the Torah and to make lawful for you some of what was forbidden to you. And I have come to you with a sign from your Lord, so fear Allah and obey me."