Think of this app as the shared whiteboard shopping list stuck to your refrigerator door, except that it's always on your phone!
With this app, you can share a single checklist among friends or family.
For instance: a packing list for a trip, a shopping list for the store, or a to/do list for chores.
You can then share these checklists amongst family and friends. Every time someone checks an item off the checklist, it's updated in real time for everyone whom the checklist is shared. Every time someone adds an item to the checklist, everyone else gets to see it as well, in real time! This prevents both of you from coming home with milk, for instance --- the first person to buy it checks it off the list and no one else will make that purchase again!
Because you have the ability to copy checklists, you can create a packing list for yourself, copy it, and share the copy with your friends so they can see what you planned to bring for the vacation. If they remember something, they can add it to the checklist so you can see what they thought of that would be useful.