For Kuleshov, the sequential juxtaposition of content lends meaning to images that may have nothing to do with each other.
And he conducted an experiment, the so-called Kuleshov effect, to highlight this principle. Kuleshov took a clip of Ivan Ilyich Mozzhukhin (the Ryan Gosling of Tsarist Russia) staring at the camera and intercut it with some other images: a bowl of soup, a girl in a coffin, an attractive woman. When he showed this sequence to an audience, the viewers noted how the emotional state of the actor changed from cut to cut. He's hungry. He's sad. He's got the hots for that lady.
The audience praised Mozzhukhin's emotive performance. But the actor's stare that Kuleshov used was the same in each cut. Here's an example of the effect: