A cat's veterinarian (vet for short) gives a cat checkups and takes care of it when it's sick, gives it shots, etc. A vet can do various things to a cat, and even give it extreme things such as surgery or neutering or spaying.
A good vet would care for a cat responsibly and carefully. The vet shouldn't hurt the cat or do anything incorrectly. Otherwise, if he/she does, this shows the veterinarian is inexperienced, or is bad and doesn't care about animals and pets. Make sure your vet would know how to care for your cat correctly.
Taking a Cat to the VetEdit
A cat is usually taken to the vet in a carrier to keep it safe. It shouldn't necassarily eat before visiting the vet. Some cats are afraid of the vet and will hiss and growl at the vet. The cat will need to get used to this to fix the issue.
When a cat needs serious care, such as surgery, an owner will have to leave the cat in the vet for a few days (if possible) or wait in the vet until the vet is finished doing what he/she did to the cat. Make sure there is nothing wrong with the cat, or the vet may have done it wrong.