Civil Law:

Further civil law is affected with violations of private rights in their corporate or individual capacity egg breach of contract, negligence, defamation, nuisance, passing off trespass to goods or the person.

Whether a person's private rights are violated then the person has a cause of action.  Hence causes of action are recognized through statutes and through the common law.  The person whose rights have been allegedly violated sues the alleged incorrect doer.  Thus civil cases are styled like Plaintiff v Defendant.  However it is his duty of the plaintiff for adduces evidence just to prove his case the burden of proof lies on the plaintiff.