At the top of the group treeview, the first two items are not actual groups but rather 2 virtual groups that include All contacts and the Current contact lookup.
What are they useful for?
Yes, it is another one of these powerful features... You can use them as any other group to create lookups.
For instance, the following scheme will reverse the current lookup, ie. it will create a lookup of the contacts not in the current lookup (this lookup scheme is available
from the Preset Lookups menu).
This one will get you the contacts that are in the current lookup but not in the Hot Deals group, maybe so that you
can add them to the Hot Deals group.