Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Personalization involves using technology to accommodate the differences between individuals. Once confined mainly to the Web, it is increasingly becoming a factor in education, healthcare (i.e. personalized medicine), and both "business to business" and "business to consumer" settings. Web pages are personalized based on the characteristics (interests, social category, context, ...) of an individual. Personalization implies that the changes are based on implicit data, such as items purchased or pages viewed. The term customization is used instead when the site only uses explicit data such as ratings or preferences.