WTFast is a GPN (gamers' private network), similar to a VPN but designed exclusively for use with video games. It's useful for improving ping, accessing region-restricted servers, and otherwise improving gameplay when one's Internet is slow or the server they want to play in is distant.
As an example, connecting directly to a server in the US from New Zealand is normally quite slow. WTFast can route your connection through a more efficient series of servers, ending at a server in the US, making your gameplay smoother than it would normally be. WTFast supports custom settings for this purpose, but by default, it uses machine learning to find the best possible route for you. Notably, WTFast has very high uptime, but it has faced competition and difficulty in some regions. Though WTFast is available in China, it has been DDoSed in that region and may be slightly less effective or available there at times.
A Quick Choice
Overall, WTFast is worth purchasing if you're a competitive gamer connecting to servers all around the world, or if you're a casual gamer living in a region where there aren't many servers. It's also useful for anyone who wants to play games with friends in distant regions.