It is a court that was established in Rome on 17 July 1998 by an international treaty called the Rome Statute.
The International Criminal Court was created to judge war crimes and crimes against humanity. Over time, the scope of its activities has expanded to include mass crimes and genocide.
The idea of creating the ICC comes from the Nuremberg tribunals, which were ad hoc, special tribunals.
There were several Nuremberg tribunals, even if the first one is the most famous, there were others. The idea behind the creation of the ICC is to formalise, institutionalise and perpetuate the nature of these special tribunals through a single jurisdiction that will be responsible for judging, at any time, the leaders of all the countries in the world who commit this kind of extraordinary crime judged at Nuremberg.
As I told you, the ICC was created by an international treaty. So the first thing that had to be done was that all the states in the world had to sign the treaty. Then, after signing it, they have to ratify it. The third step is that the treaty must enter into force. An international treaty cannot enter into force if it does not obtain a minimum number of ratifications. In the case of the Rome Statute, the minimum number of ratifications was set at 60. This minimum number was achieved in 2002. So, since 2002, the Rome Statute has entered into force and so has the International Criminal Court.
However, it should be noted that only those States that have signed and ratified the treaty recognize the jurisdiction of the ICC. In other words, only those States that have signed and ratified the treaty are part of the Rome Statute. In other words, only those States that have signed and ratified the treaty are subject to the jurisdiction of the International Criminal Court.
The difference between signing and ratifying a treaty is that the supreme representatives of the state, through its executive branch, are empowered to sign a treaty, but its ratification is done by the parliament, i.e. the legislative body representing the people. This is how it is done in most countries of the world.