Contribute to issue #15580
- [ ] closes #15580
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

I'm new at contributing on Pandas and any project at all, and saw this generic "fix docs" issue. I made some very small changes that i think it helps users to understand better the `groupBy` usage. Please, feel free to judge my changes and request modifications. Thanks!
Thanks for the PR! I don't think we want to merge any of these changes though so going to close this one.

We definitely appreciate contributions so if you are interested in the area I would suggest checking the issue tracker for items labeled `good first issue` and/or `docs` - those are a great place to start contributing