DOC: Add explanation of index to 10min tutorial table-oriented section

[Hasan-8326]

• Added a brief explanation of the index after creating the first DataFrame
• Improved the Series explanation to clarify the role of the index
• Added a reference link to the indexing and selecting data user guide section

This update addresses Issue #62358.

[mroeschke]

Thanks for the pull request, but we have others already working on this issue in #62466 and #62565 so closing this for now to let those contributors a chance for finish