What services does a doctor provide?
it depends on what doctor you are
there is a heart doctor, blood doctor, dental doctor, eyes doc., hair/skin doctor, lung doctor, genes doctor, glands/hormones, psychological, etc.
Depending on what kind of doctor you are, it also depends on what kind of care you give to the patients.
In the USA when you have an stroke you qualify automatically for medicare and medicaid, once you have theses you choose for a specific health insurance company. You will need a referral from your doctor for specific services you might need, but you can also call medicare and medicaid directly and they provide some services themselves.
A veterinarian is a doctor, so in that respect they are the same. However, if you are asking what the difference between a human physician and a veterinarian, the major difference is in species treated. Human physicians (MD/DO degree) are legally only allowed to provide medical services to humans; veterinarians (DVM/VMD degree) are legally only allowed to provide medical services to non-human animals.
Can a security services contractor provide security patrol services to a business on a contractual basis?
Governments provide road building and maintenance, protection, legal services and investigation operations and incarceration facilities, educational services, health services, social services, legislation and law interpretation, water and sewage services, some provide fire, ambulance and other emergency services ... security