菜鸟求助有关阀门的压力问题

看资料时发现很多有关压力的短语，现在是越来越糊涂，请哪位大侠能用最通俗的语言给我解释一下其大概的含义，万分感谢：

Operating Pressure

Differential Pressure

Differential for Quiet Water Service

Close-off Pressure