Veterinary assisting is an entry level-position in a veterinary facility. There are no special education or training requirements for this position in any state in the US. Training si typically done on the job. Because most training is done on the job it is often very cursory and lacks the depth and breadth of a formal education. Veterinary assistants are generally taught the basic how-to but not the why or when you would do something different. They tend to do basic tasks such as animal restraint, basic care and sanitation, assist in patient monitoring, prepare instruments for use in surgeries or daily treatments, they may give medication as prescribed by the veterinarian, collect biological samples and perform basic diagnostic tests like reading fecals. Veterinary assistants are generally not the equivalent of a formally educated veterinary technician. For example, many assistants can place an IV catheter and hook up a fluid line to it, but they generally don't know how to calculate the appropriate amount of fluids to give in a 24 hour period to maintain hydration, replace lost fluids from vomiting/diarrhea, calculate the appropriate number of drops per hour to provide the correct amount of fluids or understand the different types of IV fluids available and when each type is appropriate to a given situation. They may monitor anesthesia but they generally don't know how the different anesthetic drugs they are giving affect the body other than producing sedation or anesthesia---do they cause a drop in blood pressure that needs to be compensated for, do they make it more likely for animals that have seizures to have one, do they need to change the anesthetic protocol to compensate for heart, liver or kidney issues in a given patient. Veterinary assistants generally require much more supervision than a credentialed veterinary technician
There are voluntary educational opportunities for veterinary assistants, however these are not equivalent to a college degree program and are instead basic vocational training. There is no over-sight by a professional body to ensure that the majority of these programs provide adequate or correct information. Many have no requirement for hands-on training and instructors often have little or no experience or education in the veterinary field. There are a handful of certification programs that are designed and approved by veterinary professional organizations or that are offered by colleges which also offer accredited veterinary technology programs and these are better choices for someone who wants to be a veterinary assistant. All of these programs offer certification as a veterinary assistant, but this certification is not legally recognized or required by any state in the US.
All that being said, veterinary assistants are an important part of the veterinary medical team because there is too much daily workload for a vet or a veterianry technician to be able to keep up with everything on their own. A veterinary assistant is another set of hands and eyes to provide care for patients and to monitor patient progress.