1、High Vacuum: This is the highest level of vacuum, characterized by extremely low pressure, typically ranging from 10^-3 to 10^-9 Pascal. In high vacuum conditions, the number of gas molecules is minimal and almost negligible. This level of vacuum is commonly used in precise scientific research, semiconductor manufacturing, and optical applications.

2、Medium Vacuum: Intermediate between high vacuum and rough vacuum, the pressure range usually falls between 10^-3 to 10^3 Pascal. In this range, there are fewer gas molecules compared to atmospheric pressure, but it is not considered high vacuum.

3、Rough Vacuum: This level of vacuum has higher pressure compared to medium vacuum, typically ranging from 1 to 10^3 Pascal. In rough vacuum conditions, there are more gas molecules present, but it is still lower than atmospheric pressure.

4、Atmospheric Pressure: This is the lowest level of vacuum, with pressure equivalent to Earth's atmospheric pressure, approximately 1013 Pascal. At this pressure, there is a significant amount of gas molecules present, and the system is not considered to be in a vacuum state.

These divisions are determined based on application requirements and system design, as different applications necessitate different levels of vacuum degree.