• Tor is a web browser made to make online browsing anonymous.
• It allows people to surf the web without leaving traces.
• Tor disguises your identity by moving your traffic across different Tor servers, and encrypting that information so that it can’t be traced back to you.
• Because Tor sends your data through lots of different servers, it’s slow, so your internet will be much more sluggish.
• Because of what Tor does it’s used for illegal purposes such as hacking, sending illegal videos, and transferring illegal documents, etc.
• Many journalists use this to protect their sources, and citizens of countries that restrict online access.
• Non-governmental organizations use Tor to allow their workers to connect to their home website while they’re in a foreign countries, without notifying everybody nearby that they’re working with that organization.

Source:https://www.torproject.org/about/overview.html.en