In camping, a sleeping pad is a simple device often used in conjunction with a sleeping bag. Its purpose is to provide padding and heat insulation. The ground may become quite cold at night, and is often covered with sticks, small rocks, and other objects that may make sleep difficult. A sleeping bag does not provide adequate protection against either hazard, but a sleeping pad does.
The simplest sleeping pads are sheets of firm plastic foam, stored in a rolled-up configuration. More expensive (also heavier) models are designed with interconnected air cells that may be compressed for maximum compactness, or inflated through a valve for maximum padding.