Notes app

Apple Notes and Google Keep do a fine job as far as notes apps go, but there’s so much more out there in this category. Consider Notion (Android/iOS), for example, which has everything you need from a notes app, plus collaboration and task management tools.
Part of the appeal of the app lies in its sheer flexibility—your notes can be as simple or as complex as you like, and everything works intuitively, as well as syncing seamlessly across devices. A $5-per-month subscription unlocks a variety of advanced features in the app.