trying to recall a regex for re.split()

[snippsat]

it says at right side "giving back as needed". what does it mean by that? what is giving what to what? how is need determined? how can a regex disable that?

It's not easy if new to to Regex and try to understand something in a advance Regex as this.
It's about the use of ? look at Greedy and lazy quantifiers,then use languages as this expanding as needed (lazy) or giving back as needed
The regex for Python,the article is for JavaScript but it explanation really good,
and Regex pattern is universal with small changes how languages implementing it.