tl/dr - if you've ever used an online wedding list it's like that but for everyone, all the time, any event.
Gift List Assist is a website where each member of a family or group can make a list of the things they'd like to receive for an occassion or event. The other members of the event can indicate that they're planning to get this for the person. This is then visible to all event members except the recipient.
This helps with:
See this story to see GLA in practice.
Potentially not everyone in your family or group will have their own account. Maybe they're too young or can't log in by themselves. In that case you can create a profile for them under your account and act on their behalf.
See this story to see how that works.