At first glance, a list might look like a trip.But there are some fundamental differences between them.
A list is not meant to be used to plan a specific trip. But you can use a list as a collection list for a longer trip.
A list has no expiration date, it will not disappear until you choose to archive it.
A list is missing some things a trip has, such as export to GPX, printing, cost sharing, task answers, weather forecast, packing list, etc.