The pericardium is a tough double layered fibroserous sac which covers the heart.
The space between the two layers of serous pericardium the pericardial cavity, is filled with serous fluid which protects the heart from any kind of external jerk or shock.
The outerside would be the Epicardium. The second layer would be the Myocardium. The last layer would be the Endocardium. There is also another layer which completely covers the heart. Its called the Percardium.
Fibrous pericardium and serous pericardium. The serous pericardium is made up of an outer parietal layer that is fused to the fibrous pericardium and an inner visceral layer (aka epicardium) that is a layer of the heart wall and adheres tightly to the heart.