The app provides you with a password generator which generates a reproducible (stateless) password out of a salt (here servicename) and your passphrase. By combining these values you can always recover your password for a specific service or account without using the same password over and over again.
The app is compatible with as well as based on https://getvau.lt. The compatibility can be turned off which enables some pages where the allowed symbols are restricted to be injected by configuration.
You can leave the domain field empty. If you are using domain based servicenames with a specific pattern it might be useful to use the domain field.
This is an Open Source app. Use it on your own behalf! It is provided with no warranties.
You might also want to try the chrome extension https://chrome.google.com/webstore/detail/easy-password-handling/fobokeococnhobjlfpkoibpjnajichnj.
You can also find the project on github: https://github.com/bgrande/pwgenerator-android.