In camping, a ground pad, sleeping pad, sleeping mat or roll mat is a simple device often used in conjunction with a sleeping bag

Sleeping bag

A sleeping bag is a protective "bag" for a person to sleep in, essentially a blanket that can be closed with a zipper or similar means, and functions as a bed in situations where a bed is unavailable . Its primary purpose is to provide warmth and thermal insulation...

. Its purpose is to provide padding and thermal insulation. All types currently available use air as their primary form of insulation

Manually Inflated

Closely related to the air mattress

Air mattress

An air mattress is an inflatable mattress/sleeping pad. Due to its buoyancy, it is also often used as a water toy/flotation device, and in UK is termed as a lilo .-For sleeping:...

 a pad of this type requires an external pressure source to inflate, typically in the form of a pump or by blowing orally. Convection of the air inside the mattress reduces the amount of insulation it provides and more complicated mattresses include methods to reduce this by either partitioning the internal cavities, or by filling the cavities with material to trap the air such as down feathers

Down feathers

The down of birds is a layer of fine feathers found under the tougher exterior feathers. Very young birds are clad only in down. Powder down is a specialized type of down found only in a few groups of birds. Down is a fine thermal insulator and padding, used in goods such as jackets, bedding,...

 or synthetic insulation.

Self Inflating

An extension on the conventional manually inflated mattress, this type is capable of self-inflation due to the open-cell foam that fills the internal cavity. For many years this design was protected by various patents held by Cascade Designs

Cascade Designs

Cascade Designs is an American company specializing in outdoor recreation products. It is located in Seattle, Washington, and was founded in 1972 by two former Boeing engineers, who were avid backpackers...

  and they were an unusual and premium item. But since these patents expired many other manufacturers are now producing this type of mattress and they are now commonplace. These mattresses are lightweight and pack to a small size, which make them popular amongst hikers and campers. A self-inflating mat typically measures 183x51x3.8 cm, weighs about 700 g, and packs to 28x16 cm.

Solid Types

Closed cell foam

Foam

-Definition:A foam is a substance that is formed by trapping gas in a liquid or solid in a divided form, i.e. by forming gas regions inside liquid regions, leading to different kinds of dispersed media...

is used to produce simple mats that do not require any inflation. Closed cell foam pads are lighter and more durable than their air-filled counterparts, as they are constructed of fewer materials. Many may also be trimmed to size should the user choose to do so. However, they are generally not as comfortable as air-filled mats because they are thinner, and may also take up more space in a pack, depending on the materials used. Variations include textured or shaped foam to increase the unrolled volume and/or change the stiffness of the mattress. This can also be used to trap the air within ridges or an egg-carton type of texture, as is the case in the Therm-a-Rest RidgeRest and Z-Lite, respectively.