Well it is available in the app store for iPhone and iPad so Apple must be happy with them, I cannot comment myself I have not used them. It is a VPN service that you can use on your Mac or iPhone/iPad. If you don't know what a VPN service is you will find info about it on their web site.
Apple makes no guarantees about an app other than it meets their submission guildelines. That doesn't mean that a given app is secure, reliable or that it delivers what it promises. There are many very negative reviews in the iTunes Store on the iOS version of app, so it should be approached with caution even for the Mac version.
It's a public VPN service. The point is to prevent other people at a hotspot from seeing your network traffic. It will do that, but the people who run the VPN server will see all the traffic, and moreover they will know your identity. How much do you trust them?
With or without a VPN, the traffic all ends up on the open Internet eventually.
If you connect only to secure websites (such as this one) and other secure services, the content of your network traffic is protected anyway.