The Wii U Pro Controller is the second controller released for the console, available separately. Like more traditional controllers, it features standard control sticks, buttons, and triggers. Nintendo unveiled the Pro Controller at E3 2012 with the aim of attracting more "hardcore" gamers to make the Wii U more competitive with Sony's and Microsoft's offering. Many video game journalists have noted the similarity between the controller and Microsoft's Xbox 360 Controller. Nintendo claims that the design of the Pro Controller is an “enhanced version” of the Wii Classic Controller and "offers a richer experience." Regardless of this, certain games with flexible control schemes, such as Call of Duty: Black Ops II and Trine 2: Director's Cut, are also compatible with the Classic Controllers. The Wii U Pro Controller, however, is not compatible with previous-generation Wii games nor with particular Wii U titles such as New Super Mario Bros. U. More examples are games that require the relation between the TV and the Gamepad screen, such as Nintendo Land and ZombiU.
Source: Wikipedia, "Wii U", available under the CC-BY-SA License.