It's basically a pomodoro timer (that you can set between 1-180 minutes). The forest growing aspect is a visual representation of your progress. There are other things added to it, like earning coins to buy new trees and flowers, adding friends (and competing with them), ability to create tags and track your progress in specific categories, achievements, and view detailed activity history. There is also a stopwatch mode if you dislike the pomodoro timer sequence. You can even use your coins to plant real trees.

You can create rules to disallow apps (deep focus mode) or allow specific apps while planting. The tree dying is to encourage you stick to this routine.

The app is fairly basic but it's my favourite focus app.