Added content to stub

[BTmathic]

Added definition, examples and some uses as well as computational info and interesting formulas that occur.

• I have read freeCodeCamp's contribution guidelines.
• My pull request has a descriptive title (not a vague title like Update index.md)
• My pull request targets the master branch of freeCodeCamp.
• None of my changes are plagiarized from another source without proper attribution.
• My article does not contain shortened URLs or affiliate links.

If your pull request closes a GitHub issue, replace the XXXXX below with the issue number.

Closes #XXXXX

[thecodingaviator]

@BTmathic Thank you for your contribution to the page! 👍
We're happy to accept these changes, and look forward to future contributions. 📝