Pandas DOC: Clarify parentheses vs. brackets

Pandas version checks

[x] I have checked that the issue still exists on the latest versions of the docs on main here

Location of the documentation

https://pandas.pydata.org/docs/dev/getting_started/intro_tutorials/index.html

Documentation problem

I teach Python and pandas to new programmers, and one of the things my students consistently get tripped up on is when to use parentheses vs. square brackets, and why. (I'm a pandas contributor, and I don't always have a good explanation about why something in pandas uses one vs. another.)

Suggested fix for documentation

I wrote up the following:

https://python-public-policy.afeld.me/en/columbia/brackets.html

pandas documentation assumes a baseline level of Python knowledge (though doesn't say that explicitly…?), so probably doesn't make sense to copy that page wholesale. I propose adapting that page to a new page/section in the Getting Started tutorials.

Looking for a 👍 from another maintainer, then happy to review a pull request from whomever is interested in picking this up!