|ab (Remember The Milk) says:|
Thanks, I might just move my answer here incase anyone else has the same question. David asked about the difference between Inviting/Sharing, and how Sharing works.
"As for your question:
Inviting someone to RTM (Contacts -> Invite Tab), means that you want to make that person aware that the site exists, you're handing over an invitation to that person to create his/her own account. They will not have any access to the site, nor will they be a 'contact' you can interact with, until they have created their own RTM account. An invite is just an email sent to the person to tell them about RTM and where they can sign up.
When you share a list with a 'contact', that person will recieve the list in their (Settings -> List Tab) with a '!' icon next to it. Selecting the list will allow them to either accept or reject the list.
If they accept the list, it will appear under (Tasks) with all their other lists and will also be in your (Tasks). From then on, yes, the two lists update simultaneously to any changes either person makes, if your 'contact' adds a task, it will be added to both lists.
This extends to as many people as you have shared the list with, if you share the list with say 10 of your 'contacts' and they all accept, any change made by any of the 10 people will be reflected on everyone's list.
Also note, that the 'contact' you want to share the list with, does NOT need to have you as a 'contact' to receive the list. If they accept the list, and you're not on their contact list, then you will be added automatically after they accept.
Hope that answers your question David, feel free to ask as many as you want."
Posted 7 years ago