Air mattresses are portable, inflatable plastic beds; many models have felt covers on the top to keep sheets and pillows from sliding around. They typically come in queen or twin sizes, and can be pumped full of air with an electric pump. Futons are similar to sofa beds; they are small couches with a wood or metal frame that can be converted into beds once the top half is laid down flat. Many futons come with removable covers -- or can be purchased separately -- that allow you to sleep on a different material at night than you sit on during the day. Futon covers are usually machine washable, come in different color and patters, and allow you to change the look of your futon whenever you want.
The firmness of an air mattress can be altered depending on the amount of air it's filled with. The more air you pump into it, the firmer it gets. Be careful, however; filling the mattress with too much could cause it to burst or give the pump an electrical short. Make sure the air stopper is secure to keep air from seeping out. Keep a vinyl patch kit handy in case you need to plug up any leaks. The firmness of futon mats on the other hand, cannot be adjusted. They're made of fabric and stuffed with cotton, foam and/or polyester padding.
Both air mattresses and futons are used to provide sleeping arrangements for guests, or for individuals who live in small spaces and frequently need to convert their area from living to sleeping quarters. You can drop a futon down from a couch to a bed, or retrieve an air mattress from a closet or drawer and pump it up. Both allow for an easy transition and handy storage. Air mattresses can also be used on camping trips; plug the pump into your car's A/C adapter and blow up the bed. You can sleep on the ground, or nestled in the back of a truck or van.
Follow directions carefully when using either an air mattress or a futon. When using an air mattress, make sure it will fit in your intended space before blowing it up. Choose the most durable model you can, to protect against accidental punctures. With a futon, make sure you know how to convert the model safely from bed to couch and back again without getting your fingers caught in any of the hinges.