In Common Law systems (e.g. UK, US, India, New Zealand) judges interpret legislation within the context of specific cases and create new legal principles that form precedents for future rulings. Common Law systems are adversarial, such that lawyers of opposing parties advocate for a case, and judges act as a non-interventionist arbiter.
In a Civil Law system (e.g. France, Germany, Indonesia, Japan) laws are primarily codified in legislation by the government, leaving limited room for judicial interpretation. Civil Law systems are inquisitorial, such that while lawyers of opposing parties present the case, judges take a more active role in investigating the case, gathering evidence, and questioning witnesses.
Juries can exist in both systems.