Explain what is acute myocardial infarction secondary to coronary atherosclerotic disease type 2 diabets?

mellitus.

There are two things to explain: one - the acute myocardial infarction and two - the fact that this is secondary to the diabetes mellitus.
First: The infarction of the myocard is the death of a portion of the heart muscle, due to the obstruction of the artery that brings blood to it. Acute means it is recently produced (there is also a chronic condition). The obstruction could be made by: a blood clot, a piece of a fatty plaque from the internal wall of the artery or a severe spasm of the artery.
Second: The obstruction described above could be the result of various risk factors, among which the diabetes mellitus is one of the most important. Actually the diabetes accelerates the rate of plaque building on the artery wall. Other factors could be: high cholesterol in blood (the "aggresive" fractions known as LDL and VLDL), high blood pressure, sedentarism, etc.

It means that sudden occlusion of coronary artery due to plaque rupture ,there is more than 20 risk factores for athrosclerosis which one of the important factores is DM

Acute myocardial infarction is another way of saying heart attack, and the fact that it's acute means it's happening right now, or it happened suddenly. That means a piece of plaque, or cholesterol build up along the inside of blood vessels, broke off and flowed into one of the blood vessels that brings oxygen to the heart muscles (coronary artery), and blocked it from getting blood flow. As the heart muscle was blocked from getting oxygen which it needs to live, it began to die. That's what a heart attack is. Type II diabetes contributes to having more plaque build up to potentially break off and form the blockage of vessels. The whole phrase means somebody had a heart attack brought on suddenly secondary to having diabetes.