In the Tent you can make basic necessities to survive on a desert island, such as Water and Ropes. You'll need a parachute cloth found on the shore to restore it, but then the Tent will serve you as a shelter and a place for making Water and Ropes.
Water is made in the Tent from Grass. To get it, tap on the Tent, then drag Grass to the center of the Tent. You can get Grass by cutting down shrubs in various locations.
Ropes are made from Grass and Flax. Flax can be grown in garden beds.