A crate is basically a dog house. Your puppy or dog can be left alone for some hours in it, either for it to sleep or to take some rest after a long play or training session. Apart from the regular training you give your dog or puppy, crate training is also essential. If this works out then it gives your pet some added flexibility within the premises.
Crate training for puppies actually helps a lot in potty training and even for adult dogs too. Think of a situation when your pet needs to be left under a veterinarian's supervision, being evacuated from home or has to travel on an airplane. This is when he would necessary need to be put into a crate.
Now it may take a while for your puppy or dog to get accustomed with the crate training for puppiesand being a part the regular training, one must keep in mind that not all dogs get used to it very easily. For puppies, it must be used as a "play-pen" only. Sometimes it's just not that easy, where if you got a dog that has already spent a while in crates or cages then this particular one may not take it easy with the new crate.