Generically speaking and presuming federal and state are essentially the same; What is the plain language purpose of the Tort Claims Act aka who does it cover in what capacities, etc?
I am curious why you say "and presuming federal and state are essentially the same," because they really are not.
Nonetheless, the FTCA operates as follows: first, there is a doctrine of sovereign immunity which disallows citizens from suing government entities without that government entities express permission. The FTCA provides the guidelines by which one can in fact file
specific types of lawsuits against a federal government entity and federal employees who have acted within the scope of employment while causing injuries, but certain strict rules must be followed.
Essentially, one must first file an administrative claim with the government entity that allegedly wronged him or her. Once six months pass with no answer or an unsatisfactory answer, the suit, pursuant to its various rules and exceptions, may then go forward.
[This is not and should not be considered legal advice. Rather, it is general educational info derived from the linked site].
The purpose of the FTCA is basically to allow people to sue the government for money damages for certain narrowly defined torts, notwithstanding sovereign immunity, which are closely analogous to actions of non-sovereigns, where a uniform rule for governmental and non-governmental actors would be useful, while regulating carefully the manner in which those suits are carried out.
The reason for sovereign immunity in the first place is that the government has such broad power that at some level, a sufficiently imaginative set of lawyers and judges could hold the government responsible for just about anything.
So, FTCA basically takes responsibility for certain kinds of routine car accidents, slip and fall situations, medical malpractice and the like, while excluding uniquely governmental discretionary functions.
The FTCA is the “exclusive means by which a party may sue the United States for money damages . . . in tort” pursuant to 28 USC § 2679, but this is really something of an exaggeration as there are lots of constitutional and statutory grounds upon which the United States government can also be sued for money damages that naively appear tort-like, such as a reverse condemnation action under the 5th Amendment to the United States Constitution.
The FTCA does not bar suits for breach of contract, does not bar suits for injunctive or declaratory relief, and does not bar suits against government employees for money damages for intentionally violating someone's civil rights (even though some union contract indemnify and defend government employees for civil rights violations, in practice, converting tort liability of an individual into contractual liability of the United States government). It also does not bar tax refund lawsuits.
In general, the FTCA relates only to the vicarious tort liability of the entity, the United States government, on a respondeat superior theory, arising from an agency or employment relationship some some other person or entity that acts on its behalf. This is because the United States government, like many entities, can't take action without acting through some other person or entity. The general agency law of state respondeat superior law determines when the action of a person or entity is attributable to the United States government or not.
Most states have similar governmental immunity statutes, although their exact details differ. The FTCA is particularly vague. Many state governmental immunity statutes are much more specific.
The FTCA itself does not govern the liability of the employee or entity which committed the tort for which the United States government is being held responsible. Not infrequently, an employee or agent who actually committed a tort (e.g. causing a car crash) can be sued in addition to a suit against the United States government under the FTCA.
Suits against the federal government for breach of contract for money damages must often be brought in the court of claims which is governed by a parallel process.