It's a torrent client that is able to download the torrent file sequentially, rather than in random chunks. Meaning you can stream a movie torrent instead of the old-fashioned method of needing to wait for the entire thing to download before you can watch. It's a combination torrent client and media player.
Any decent torrent client (apart from Transmission?) has had sequential downloading for years. It was never a unique feature of those idiot-oriented wrappers.
Popcorn Time is 10 years old. Sequential downloading wasn't as common then, and the torrenting community had very mixed feelings about integrating sequential downloads at the time. It was (still is) good for leechers and bad for seeders.
It is a tool. “Good” and “bad” are views of that tool that humans have. If two or more people are fine with transferring the pieces sequentially, there is nothing wrong with that, and no “hurting” of any “network” happens. Setting it as default for every user of some client would be bad on average, and bittorrent has enough math to ensure balanced distribution of pieces in various common and corner cases by default. However, it is quite irrelevant for torrents with hundreds or thousands of peers. They don't have availability problems, and the fairness of data downloaded and uploaded depends on too many random factors anyway. Say, if you have a client seeding just a couple of torrents which connects to peers quickly, and I have a client with a lot of torrents, and slow peer rotation, you are going to serve more data to more peers than me on the same torrent. 20 year old discussions reasoning about possible peers with modem speeds and metered connections are not completely correct today. You probably need to have terabytes of data to transfer to start caring about which approach is more fault tolerant and more fair, or notice the difference.
Well it combines website lookup + bittorrent client + viewer. If you're happy with apps that you use for that then popcorn time doesn't really bring anything to the table except the all-in-one solution.
