iCloud: What is iCloud Reminders?
You can create and manage to-do items and organize them into lists using Reminders on iCloud.com. You can also share reminder lists with other iCloud users.
Changes you make to reminders and reminder lists automatically appear on each of your iOS devices and computers that have Reminders turned on (or Tasks on a Windows computer).
Reminders also appear in Notification Center on iOS devices and Mac computers.
To use iCloud Reminders, go to icloud.com/reminders and sign in with your Apple ID (if you’re not signed in already).
If you don’t see Reminders on iCloud.com, your account just has access to iCloud web-only features. To gain access to iCloud Reminders and other iCloud features, set up iCloud on your iOS device or Mac.
If you’re using another iCloud app, click the app’s name at the top of the iCloud.com window, then click Reminders.
When working with iCloud Reminders, make sure you use a browser recommended in the Apple Support article System requirements for iCloud.