If you make something like new, you renew it. When you catch up with an old friend you haven't seen in a long time, you renew your friendship.
To renew is to make new again. If you get a new due date for your library books, you've renewed them. If you forget to renew them, your books will be overdue, and you may have to pay a fine. Renew also means to revive, restore, or cause to appear in a new form. Historically, all kinds of tonics have claimed to renew a person's health, but many of the early ones actually contained poisons that could kill you.