The way the app works is extremely simple. You just have to enter your email account to see a list of websites where you've used it to register and that have suffered any type of hacking or security breech.
Among the findings, you can see if you've suffered any data theft stemming from known scandals related to Adobe, LinkedIn, Tumblr, Yahoo, or Dropbox among many others. You can see the date the incident occurred, a description of what happened, along with the severity of the information taken.
have i been pwned is a useful tool that, while it doesn't offer a system of protection or perform any task actively, it can help by letting you know if it's time to change your passwords and login information.
Requires Android 4.4 or higher.