The picture shows what I mean by "block" - I mean a cell of code that is delimited by some sequence of characters, in this case '#%%', that can be executed by the python/IPython console when the user types some keybinding while the cursor is in that cell.
It's very useful for interactive/explorative work because you can break your code up into logical chunks where each part can be worked on iteratively without running the entire script each time.
So if one part of my code ingests a large data frame and another part analyzes it, I can put each part in different cells so that while I'm playing around with how to best interpret the data I don't have to keep reloading the data frame on each iteration.
If emacs can do this kind of block/cell execution, I will wholly devote myself to its religion. Right now I know of a few possible ways in vim, but suffice it to say they are all terrible.