A shelter, or a tarp, protects you against rain without you having to retreat into the tent. It is no fun if you have to shut out nature just because of some rain, and with a tarp you don’t have to. Outnorth have super-lightweight shelters from brands like Hilleberg
A tarp works well against rain, but it can also protect you against the sun. A lot of people prefer to sleep outside for real, and that makes a tarp the perfect accessory. You will definitely get the feeling of actually sleeping outside, but you are protected against possible rainfall during the night. It’s just the imagination who sets the limit for how you use your shelter. It could be a great extension of the tent entrance, or you could gather under it if you are traveling as a larger group. If you want to make food outside, away from the tent, a tarp is just perfect and will shelter you against the rain.
Shelter vs. tent
It can be cozy to crawl into a tent, but that often means lights out or at least the end of all social interaction with the outside world. With a tarp you shut out the bad weather, but you don’t shut yourself in. As a complement to the tent, the tarp is a perfect place to set up camp.