There are examples of constitutions in governments all over the world. Essentially every government in the world has a constitution. In the United States, there is a constitution for the federal government. At the same time, each of the fifty states has its own constitution. This means that there are examples of constitutions in essentially every government in the world.
The main implication of a constitution is that there are limits on what governments can do. In the days before written constitutions, governments could effectively do whatever they wanted and were able to do. That is, there was nothing that was illegal for the government to do. There might be things it was not capable of going, but there was nothing that a government was not legally allowed to do.
With constitutions, governments are subject to the rule of law just as people are. Constitutions are laws that governments must obey. In the United States, for example, the president cannot simply pass a law on his (or someday her) own because the Constitution says that is illegal. The government cannot take away our property without the due process of the law. These are things that are illegal because the Constitution says so.
Thus, the main implication of a constitution is that government is limited and cannot simply do whatever it wishes.