A handy feature in the new Reminders app is the ability to share your lists with others. This means that the people you specify can read, add items to or delete items from your iCloud lists. A perfect use for this might be sharing a grocery list with members of your family or a To-Do list with members of your project team.
As far as I know, the only way to instigate the sharing of a list is from the Reminders app on your Mac — I have not noticed any way to do so on an iOS device. You can, however, access shared lists on your iOS devices.
The procedure for adding someone to a Reminder list is as follows:
1. Open the Reminders application on your Mac.
2. Move your mouse pointer over the list you wish to share until the share icon appears.
3. Click the icon to the right of the list name.
4. Enter the e-mail addresses of everyone with whom want to share your list
That’s it! Your recipients will receive an e-mail prompting them to join your list. Note that in order to join a list, the recipients must have an Apple ID.