The animation in the start of the page load, that comes from bottom to top. The whole slides bottom to top but in 6 different frames.
Different ways to build this.
Each of the black bars is set to a 20% width and height that fills the viewport. Possibly fixed to the top with their point of origin set to the top.
Possibly a size interaction where the height changes from 100% (if contained in a 100vh height parent) or 100vh themselves. Changes to 0vh or 0% in height.
The interaction timing is staggered in a way that creates the step effect.