交互项的意思是，一个变量通过另一个变量影响y

那就是说没有直接影响Y，需要通过另一个变量来影响Y，也就是增量影响的意思吗？谢谢

不仅可以直接影响y，还可以通过另一个变量间接影响y

Let me use part of your model to explain the interaction effect.

(1) CARi=a+b0ESi
(2) CARi=a+b0ESi+b1ESi*NASi

Model (1) assume that ESi has a certain unit effect on CARi. When ESi increases by 1 unit, CARi will alter by b0 correspondingly.

Model (2) assume that ESi has a effect on CARi, however, the degree of the effect is based on NASi. If NASi is fixed, ESi remains the unit effect b0. If NASi varies alongside the ESi, the effect is the joint function of b0 and b1.

Hope this is clear for you.

Thank you, it's very clear!