Generally speaking, judicial activism is the opposite of judicial restraint in that when a judge is especially "active," he or she imposes more of his or her own will in the case, whereas if a judge is more "restrained," they rely more on precedent.
If a court is exercising judicial activism, it means the court is actively making rulings that will change the laws that have been established by other branches of government, and even sometimes by other courts. The use of the word activism refers to the belief that the judges who behave in this manner are serving as activists who are pushing forward personal or political agendas.
Judicial restraint, on the other hand, means that the members of the judicial branch are restraining themselves from making decisions that could end up changing policies or laws.
