Nyaa Pantsu is a new torrent tracker and a replacement for the now defunct Nyaa.se.
As you have likely heard, Nyaa willingly went offline on May 1, 2017. The tracker was so ubiquitous that a noticeable vacuum appeared in its place once it left.
The same can be said for BakaBT, although that tracker has gone private rather than offline.
Still, Nyaa was more popular because of its relaxed rules when it came to content SFW and otherwise and seeding.
Nyaa Pantsu hopes to continue where Nyaa left off. According to the FAQ, not everything from Nyaa was lost. It has a database of torrents up through May 1 and another database for sukebei (18)+ torrents through 2016. The founder hopes that a newer database for sukebei will become available for use.
The tracker currently has search functionality and seeder/leecher statistics are possible by scraping. The statistics may be restored at a later time.
Torrents will still work as long as long as the file is listed on the DHT network. For now, it appears that users are limited to magnet links and not actual torrent files.
You’ll also find other information on the FAQ, such as how-to-help section and a list of recommended trackers in the case an upload is denied.