A more thorough explanation:

In Public international law, the subjects of international law traditionally included states. This means that countries are considered as subjects of international law. However, since the establishment of international criminal tribunals, individuals are also proper subjects of international law. This means that people can also be held accountable for their actions in the international sphere.

Other international actors include transnational corporations, nonstate actors, and terrorist groups. These are entities that operate across borders and have an impact on the international community. The regulation of these actors' activities in the international sphere is one of the most pressing concerns of contemporary international law.

For example, a transnational corporation like Coca-Cola operates in many countries around the world. Its actions can have an impact on the environment, human rights, and the economy of those countries. Therefore, it is important to regulate the activities of such corporations in the international sphere.

Similarly, nonstate actors like NGOs (non-governmental organizations) and civil society groups also play an important role in international law. They can advocate for human rights, environmental protection, and other issues that affect people around the world.

Terrorist groups like ISIS (Islamic State of Iraq and Syria) are also considered as subjects of international law. Their actions can have an impact on the security and stability of countries around the world. Therefore, it is important to hold them accountable for their actions in the international sphere.