Tor’s claim to fame is that it allows users to browse the web anonymously. It redirects traffic through a network of relays to prevent the activity from being tracked. In order for this to work on Android, users are required to download Orbot, which is a proxy app. It works in conjunction with the Tor Browser to connect to the Tor network.
It’s worth noting that this is an alpha release. Tor hopes to not need the separate Orbot app in the future. Also, if you have been using Orfox, a browser that utilizes the Tor network, it will be sunsetted in favor of the official Tor browser. The stable release is pegged for 2019.