What is swags?
Austrailian for Bivy essentially. They are a bit bigger so you have more room for boots and a small pack.
Usually, they have mesh openings on the ends so you can get good ventilation in the rain as the fabric bellows out. They also can have mesh top sections as well for star gazing and ventilation as well. Add a ~3" foam mattress included in some, and you have a really nice compact sleep system with a bit of room to move around in a limited way.