You may be wondering how you can distinguish a choker from a collar. Well, in reality, there is a lot of overlapping in style. You may look on one department store's site and find what they are calling a collar, being described as a choker on another site.
Simply, a choker is a short necklace, worn close at the neck. This style, which was also known as a 'dog collar', was typically constructed of pearls and fine gemstones and became the look of the day during the early 1900 Edwardian period.
Previously, these snug fitting neck adornments were made of a band of velvet or lace cloth often embellished with jewels, but due to King Edward's wife, Queen Alexandra, attempting to hide a scar on her neck, her use of choker style necklaces brought the dog collar into the height of fashion.
In modern days, styles that are considered to be chokers can range anywhere from 14 inches up to about 16 inches in diameter. This style that Queen Alexandra is wearing is normally called a choker in our day and time; (dog) collar is not usually the term we use for this close-aroumd-the-neck style.
Chokers are so varied in today's jewelry world! They may be made of metals, fabrics, pearls, or other types of beadwork. Many do not hug the neck but lay gracefully upon the collarbone, thusly often being called 'collars' instead of chokers. Here is an example of one such piece. I normally call this type of jewelry a collar but don't be surprised if you see it being referred to as a choker on some jewelry sites!
Another style that often comes into the mix that's also a shorter style necklace that lays at the collar bone is a 'bib' necklace. These are sometimes called 'collarettes' and frequently have decorative embellishments flowing down the front. These can be quite the statement pieces due to the ornate nature of the decorations draping from the high neck collared piece.
I hope this brief summary of collars and chokers has helped you see the differences - and the similarities - between this type of jewelry. When it's all said and done, many people just use 'choker' as a general term that helps categorize the types of necklaces that lie close to the chin.