The chin rest that comes on the top of your violin is removable and customizable. It is more common than it used to be to switch out the chin rest for a different style if you prefer. The chin rest can make a big difference for the comfort of your neck and shoulders. You can choose a chin rest that sits either on the shoulder of the violin, in the center over the tailpiece, or between the two.
A smaller person with smaller shoulders will be more comfortable with their head closer to the middle of the instrument. A large person with large shoulders may be fine with the traditional placement on the side. It also depends how much you turn your head when you play, and on the shape of your neck and your instrument.
Chin rests can be different heights to accommodate different neck lengths. Someone with a very short neck will want a chin rest with as little height as possible, and sometimes they prefer none. But if you have a medium to long neck, you can take up the space with a raised chin rest, or a raised shoulder rest, or you can split the difference.
A chin rest may have a lip or bump that can dig into the neck. The bump is there to lock the violin under your chin, with the raised section braced against your jawbone to make it secure. This can cause discomfort and excess rubbing. I would generally avoid this type of chin rest.
The Wittner is a best-seller because it is designed to be as comfortable and non-irritating as possible.
This is a standard chin rest on the left side of the violin body with a flat plate extending over the end button. I use this chinrest.
This Wittner variant sits in the middle, great for players with smaller shoulders or larger instruments. You can buy risers to raise it up for a long neck.
This chin rest allows for a variety of positions of the chin and jaw. Very comfortable and secure.