Crate Training is a method that is commonly used to house train dogs. A crate (cage) is normally constructed from plastic or metal and comes in a wide range of sizes to fit all dog breeds. Crate training dogs is considered to have positive results for both the dog and its master.
The reason crate training works so well is that most dogs don't use their sleeping area as a toilet. Given that in most cases the crate will serve as a sleeping area for your dog, the dog learns how to resist going to the toilet until they are out of the crate.
During crate training, one of the fundamental rules is that your puppy/dog needs to stay inside the crate at all times except when they are feeding or when they are let out to play. When you do let your puppy free from the crate you should take it outside immediately so it can relieve itself.
Your dogs crate should be about one and a half times its body length and slightly higher than your dog in its standing position. If your crate is too long it is recommended that you block of one end. Excess space can act as a bathroom for you dog so it shouldn't be permitted. Plastic crates are the most popular these days as they are durable and very easy to clean.
You should take your puppy to the toilet fairly regularly during the crate training period. As your puppy grows you can reduce the number of times it is let out of the crate each day as it will get used to holding its urges to go to the toilet.
Ideally your puppy should see the crate in a positive light. You can build up this positive association by feeding you dog inside or close to the crate. Also make the crate more enjoyable by putting your puppies most loved toys inside there. To further grow the positive view of the crate, give all your dogs good behaviour rewards to your dog inside the crate.
Never use your dogs crate as a place of punishment or a prison. Dogs shouldn't be locked in crates for long periods of time as this can make them take a disliking to the crate. Don't leave your dog in its crate when you are not at home.
Crates are useful tools for transporting your dog or puppy be it in the car or in airplane. All airlines now require dogs travel in quality dog crates.
Not everyone is a fan of crate training. Some professional trainers look down on the method sighting that dogs can become too emotionally attached to their crates after being locked inside them for long periods of time.
Below is a link that has much more information about how to train dogs and puppies in a number of situations, as well as more information about crate training.