The image above will link you to the Tor Project's website. Tor, or The Onion Router, is used to encrypt your information and bounce your signal between multiple different servers as explained here. Tor is one of the most popular softwares used to navigate the Dark Web, however does not guarantee complete animinoty and precautions should be used to ensure safe and secure navigation of the Dark Web.
Tor, however, is only the software that will get you onto the Dark Web. However there are other services that will help you navigate the Dark Web as well as the Deep Web.
The Deep Web: The Deep Web does not require the use of Tor or router-bouncing softwares to navigate, however it is often called the "Invisible" or "Hidden" Web because it is password protection or requires authority from a different server. For example, Facebook.com can be easily accessed from the Surface Web, however your personal Facebook profile's editting features are not because they are password protected. Other examples of the Deep Web included medical databases and scientific data.
The Dark Web: This does require Tor to use and the content found on this can be explored further in the benefits and dangers sections.
Below are images that show how much activity really does go on on the Dark Web as of 2011 and the growth since then:
Figure 1. Estimated number of bridge clients on December 5th, 2011 by country. A bridge is a relay whose existence is non-public and can provide access for blocked clients, often with pluggable transports, which registers itself with the bridge authority. Bridges are smaller in number than relays and offer a way to access Tor without using relays due to being unpublished or non-public.
Figure 2. Estimated Number of Relay Clients on December 5th, 2011 by Country. Relays are publicly-listed nodes in the Tor network that forward traffic on behalf of clients and register themselves with the directory authorities. Relays are a good way to gauge the amount of traffic or people that are accessing the Tor network, but the list of relays can be publicly accessed, so theoretically access to Tor could get blocked.
Figure 3. Estimated number of bridge clients on December 5th, 2016 by country. A bridge is a relay whose existence is non-public and can provide access for blocked clients, often with pluggable transports, which registers itself with the bridge authority. Bridges are smaller in number than relays and offer a way to access Tor without using relays due to being unpublished or non-public.
Figure 4. Estimated number of relay clients on December 5th, 2016 by country. Relays are publicly-listed nodes in the Tor network that forward traffic on behalf of clients and register themselves with the directory authorities. Relays are a good way to gauge the amount of traffic or people that are accessing the Tor network, but the list of relays can be publicly accessed, so theoretically access to Tor could get blocked.