The phrase 'common law' has different meanings, depending on the context in which it is used.
In one sense, common law refers to the laws that were originally developed in England and which have been adopted by many other modern countries, including Australia. Common law in this sense is distinguished from legal systems based on the civil law, which originated in ancient Rome.
Used in a different context, common law means law made by the courts (case law) as distinct from legislation. The phrase common law can also be used to distinguish case law that originated in the old common law courts from 'equity' which is the case law that originated in the old courts of equity.