its an anonymizing tool like tor, but i2p supports bittorrent while tor does not. theirs also .i2p site like tor .onion sites. also i2p is peer to peer while tor is volunteer run with the tor project managing the network.
usenet for bulk current media, occasionally torrents for niche stuff, but now that rarbg is gone I'm going to have to find a new tracker. I use a seedbox for most torrent activity these days as well, too risky with ISPs clamping down.
Once upon a time I used DC++ for things, but that was more than a decade ago and the last time I tried it all the severs seems to be in eastern eu countries and very shady. If anyone knows a good DC++ server I'd love to hear more.