Dog collars come in several designs with the four most popular being the standard collar, martingale, half-check, and choke. Each collar offers several different advantages and is used for different things.
Most dogs adapt to a standard collar fairly easily. A strip of material – anything from leather, to nylon, to other bite resistant fabrics – wraps around the dog's neck. Collars typically come with a small metal loop near the front that allows you to attach a leash and a dog tag. For smaller dogs, collars with bells are popular as it lessens the likelihood that they'll sneak up on you and get stepped on. Standard collars don't have any special features that help with training, and are generally seen on dogs that are already well-behaved or have finished being trained.
The martingale collar is most commonly seen on greyhounds, and is designed for any breed of dog which has a head smaller than its neck. Unlike a standard collar which the dog can slip off, the martingale collar tightens whenever the dog attempts to remove it. When the dog stops trying to free themselves from the collar, it loosens. Martingale collars are considered to be more humane than choke collars, as the risk of injury is minimal. In fact, the collar is designed to train the dog while also maintaining its physical safety.
When a dog is having a tough time adapting to life on a leash, the half-check collar is a popular option. Similar in function to a martingale collar, the half-check design tightens when the dog either tries to remove the collar or pulls away from the leash. When the dog stops struggling, the collar loosens. The design is relatively simple, part fabric and part chain. The collar is designed to promote good behavior while not risking injury to the dog, as a choke collar might. While many owners switch to a standard collar after the training period is over, the half-check collar remains popular for those dogs who repeatedly try to remove their own collars.
Small metal links make up a choke collar. The collar sits high, just behind the ears of the dog. Traditionally, the choke collar is used as a method of training more difficult dogs, as it's designed to tighten around the dog's neck. The main difference between a choke collar and a martingale collar is that the owner has no control over how much a choke collar tightens, which can lead to health problems such as fainting, nerve damage, and death in the hands of an inexperienced owner. The Humane Society recommends avoiding the use of choke collars unless you're an experienced trainer and know how to properly size and use one.