This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
It's part of the <servlet-mapping> section. There is a link to the servlet spec in my signature. If you download it and search for either url-pattern or servlet-mapping, you will find the section that describes them in detail.