We believe that you are more than just a number. You have special interests and expertise. Your topics reflect your areas of influence. For example, you may be influential in cars while your friend maybe influential in food. Klout generates topics for you based on content that receives engagement from people in your network. You can also add topics to your Klout profile if you feel that your influence in a given area isn't represented or remove topics you don't feel are appropriate.
Learn more about Topics here: http://klout.com/#/understand/topics