Intra is an Android application that allows you to access the internet in a secure way. Developed by Jigsaw, a technology incubator within Alphabet (Google), the application protects you from DNS manipulations preventing you from accessing certain websites or applications.
A DNS is like an address book. It lists a series of IP addresses and the domain names attached to them. For google.fr, for example, the IP address is 216.58.198.195. When you enter google's URL in your navigation bar, the DNS will redirect your query to this IP address. Unfortunately, it is possible that your ISP, government, or other entity may be manipulating your DNS by changing or deleting entries. If they wish, they can change the information so that when you enter the url google.fr you are no longer redirected to Google, but to Facebook or simply by not redirecting your query.
This is where Intra comes into play. If you want to use another DNS, on your smartphone/tablet, the application allows you to change it and use another one. You can, for example, use Google's public DNS or Cloudflare's DNS which are recognized and secure DNS.
Intra is completely free, open source and downloadable on Google Play.