The History of English Common Law

Common law, also known as case law or precedent, is law developed by judges through decisions of courts and similar tribunals, as opposed to statutes adopted through the legislative process or regulations issued by the executive branch.
A "common law system" is a legal system that gives great precedential weight to common law, on the principle that it is unfair to treat similar facts differently on different occasions. The body of precedent is called "common law" and it binds future decisions. In cases where the parties disagree on what the law is, a common law court looks to past precedential decisions of relevant courts.