The Invisible Internet project (I2p) is a low latency 'garlic routing' network intended to provide anonymous and censorship resistant communication between users of the network. Unlike tor, i2p is not intended to facilitate access to the 'clear net' and, although this is possible through use of an 'outproxy' bridge to the internet, tor is more suited to this use. Popular uses for i2p include anonymous websites, irc chat, 'email' style messaging, bittorrent and other p2p file sharing.
You can find a list of supported applications here https://geti2p.net/en/docs/applications/supported#decentralized-file-storage
To get started with i2p download the installation package from https://geti2p.net/en/download and follow the instructions on that page to to up and running.
A quick and dirty getting started might look like.
1. Download i2p from here https://geti2p.net/en/download and installation
2. Start i2p using “i2prouter start” in a terminal
3. In your browser head over to the router console at http://127.0.0.1:7765 and make sure everything is working, forward ports if necessary and adjust the bandwidth setting
4. Configure your browser proxy setting to point at the router “ http = 127.0.0.1:4444” https = “127.0.0.1:4445”
5. You can now browse eepsites
6. You can find some basic links on the router console page. At the very least you probably want to install noscript (before changing the proxy settings) or disable javascript altogether
For more info about i2p see
https://geti2p.net/en/about/intro
https://geti2p.net/en/docs