There are three main systems in use throughout the world, namely Civil (Roman) Law, Sharia (Muslim) Law and Common (Anglo-Saxon) Law. Most Civil Law systems use juries, some Common Law ones do not (eg India and Pakistan).
Civil Law (used in 90 countries) is based on the Corpus Civilis Juris (codification of Roman law) promulgated by Emperor Justinian the Great in 529-34AD. Its rules were applied by European courts with no binding precedent case law. Then in the 19th Century it was incorporated into national codes, starting with the seminal Code Napoleon of 1804. It has been adopted throughout Asia (including China, Japan and Turkey), Francophone Africa and Latin America. It is easy to export, as all that is necessary is to promulgate legal codes. Unlike Common Law, no corpus of decisions in leading cases is necessary because Civil Law is based on principles, not precedent (although it does use case law as an indirect source). Unlike adversarial Common Law trials, it has judge-led inquisitorial hearings.
Sharia Law is based on the Qur’an (632 CE) and Hadiths (rival Shia and Sunni versions) circa 900AD. It was adopted by every Islamic jurisdiction, but most have, however, since modified it by importing some Civil Law law codes (eg Egypt, Tunisia). Similarly some Common Law countries have readopted some Sharia Law (eg Malaysia, Northern Nigeria and Pakistan). As a result, there are few pure Sharia Law countries. Even Saudi Arabia has adopted some Civil Law.
Common Law (used in 40 countries) is grounded on the 1166 Assize of Clarendon. Henry II, King of England, was disturbed by the fact that local courts were applying different laws. He, therefore, sent judges from the Court of King’s Bench on circuit throughout the realm applying a common system based on binding case law precedent (not Roman Law principles). The British Empire spread the system throughout Africa, Australasia, North America, and South Asia. Civil Law countries which fell under Anglo-Saxon control had Common Law superimposed, thereby creating hybrid systems such as the Channel Islands, Louisiana, Philippines, Quebec, Scotland, South Africa, Sri Lanka. Now (2016) some jurisdictions (such as Kazakhstan and United Arab Emirates) are adopting the English law of contract, ie importing some common law.