The Kuleshov effect is about how two images are automatically connected in our minds, given them a “combined” meaning , or how one influences the other.
Ex:. The exact same picture of a person is exhibited followed by 3 different ones. The human mind links them automatically. Like they was somehow one, or both images belonged in the same composition. The viewer then assumes that any facial expression showed by the person in picture 1 is a normal or expected reactions to the second image.
Heres a link to a video of the Kuleshov effect explained by Alfred Hitchcock. The effect is acknowledged and used to manipulate the perception of viewer towards the character. The same reaction occurs in the character, but the images that follows change. Our mind connects them, and we automatically make a judgment about him, based on what we find acceptable/expected/socially standardised. This video showed that beyond knowing how to use the effect is important to know the audience (age, culture, religion, sex) we are trying to communicate. And therefore we will be able to use the effect in a more “targeted” manner.