Puppy playpens provide a perfect space for a pet, they are somewhere safe and secure to put your dog while you are busy doing something such as ironing, washing or just general jobs and do not want your puppy running around your feet all the time and at inconvenient moments. That is not the only use for a playpen it can sometimes provide a space for the animal when something is going on they do not like, for example a couple of guests visiting all the new smells and sounds can become a bit overpowering for a young dog that is unsure and nervous.
With time the pen will become a place of security and your dog will go of his or her own accord and it will just become the standard reaction they develop to new situations and could even stop barking so much, not completely but it could have a beneficial effect on the behaviour of your dog. They are normally made from metal bars on four sides and a barred roof while this sounds crude it is just the most effective form for a dog cage there is also normally a door on the side that is secured with an outward bolt allowing you to quickly open and close the door as you need.
When buying a puppy playpen it can be a good idea to shop around for the best deal, there are numerous places that sell them so prices will differ and you could even find yourself a good deal if you look hard enough. Remember to be sure it is of a good size and you have somewhere to put it as well as it being the right one for both you and your dog.