A handoff is a changeover: the moment a child moves between homes. Once your custody schedule is set, handoffs are generated from it — you don't add them one by one.
Each handoff shows the time, the place if you've set one, and which child. Both parents see the same list.
Handoffs are the single most argued-about part of co-parenting, and almost always about detail rather than bad faith. A shared list that says 6:00 at the library removes most of it.