Reminders is a component of iOS and macOS that allows users to set notifications for themselves and create lists. It was a new feature in iOS 5 and OS X 10.8 "Mountain Lion". It can sync data between iOS and OS X through iCloud.
Use Reminders for projects, groceries, and anything else that you want to keep track of. You can set when and where you want to be reminded. You can also remind yourself to get back to something you’re doing in another app. And with iCloud, you can keep your reminders up to date across all of your devices.