Reading: Digital identity
Digital Identity 
Identity has many components: who you are and what you do are the sum of your characteristics, including your place and date of birth, your education, your preferences, tastes, and so on. Some of those characteristics never change, while others change over time, such as your hairstyle or job.
Similarly, your online identity is the sum of your features and interactions as they appear on the web. Because you interact differently with each website you visit, each of those websites will have a different picture of who you are and what you do.
It is important to understand the differences between your online and offline identities because your online “representation” often differs from your characteristics in the physical world. Your online “persona” is made of all the components of your identities produced by the websites you interact with: Amazon builds a partial identity of yours based on the products you like and buy, eToro based on the stocks you follow or own, and so on. Some of the information associated with these partial identities is under your control, may be out of your control or might even be invisible to you.
Every time you use a service like Google or Facebook, for example, your browser stores cookies, and these act as identifiers that connect all your characteristics into a general online identity. It is important to understand that these characteristics often do not refer to you as a person with name and surname, they simply point to a set of characteristics that have been collected about your profile. Web companies such as Google use these aggregated data to present you targeted ads, and thanks to this can provide services such as Gmail for free. This is called behavioural targeting: companies make money by selling advertisements targeted specifically at people like you. Think about it: if you do not pay for the product, in many cases you (and your personal data and identity) are the product… Another reason for which some websites build a profile about you is security: web services such as your bank have concerns about online frauds, and by profiling your interactions with them, they can notice changes in your behaviour and act accordingly to protect your interests.
Indeed your online identity, as well as all your online “partial identities”, have a value. This is true not only for online identities connected to your bank but also for your activities on social networking sites, whose value may be less tangible but equally important. Simply by being an active Internet user, you accumulate many online partial identities: as the value of your partial identities grows, the information becomes more attractive both to web companies and to identity thieves. At the same time, since each of your online partial identities may contain very private information, protecting yourself from a loss of privacy is equally important.
 This text is partially adapted from: Internet Society (2016). Policy Brief: Identity in the Internet.