“Tor — an acronym for The Onion Router — is a freely available, open-source program developed by the U.S. Navy about a decade ago. A browser plug-in, it thwarts online traffic analysis and related forms of Internet surveillance by sending your data packets through different routers around the world. As each packet moves from one router to the next, it is encoded with encrypted routing information, and the previous layer of such information is peeled away — hence the “onion” in the name.” - PAUL CESARINI

There are many reasons Tor can be used for; Preventing Amazon from learning your preferences and dynamically charging you by learning your buying habits, journalist in oppressed states where there is no free speech can use it to access news from the outside and so on..

Tor [website]