This massive growth and interaction on the social web is leading the way to understand these individuals. Like in a society there are influencers, the same phenomenon is getting replicated on the social web. There are people who have more influence over other users. The process of finding influencers and calculating influence is becoming an important science. If you have used a service called Klout, you'll know what we are talking about. Klout gives a 'social influence score' based on your social media activities. There are questions about the relevance of such scores, but that's only because the influence of a person is a very relative topic. In fact, in our view, no one is an influencer while everyone's an influencer. This can sound very confusing but what we are trying to say is that influence is relative. Someone who is an influencer to you may not be an influencer to another. If you need admission of your child to a school, the principal of the school is an influencer, but if you are seeking admission to a university, the same principal is not an influencer to you. This confusion makes the topic super exciting; trying to understand human dynamics and then figuring out who influences whom and how. Merely having thousands of followers on Twitter doesn't make one an influencer but the influencer of his or her followers and the way they are influenced to take action, sure does. Our book will not get into detailed aspects of influence but it's important to keep in mind this notion while trying to understand social media analytics.