What are parallel tasks in the Critical Path?

Assignment:
Review the article below:
Critical Path – A Project Management Essential
URL:
https://www.wrike.com/blog/critical-path-is-easy-a…
1) Summarize the article. Do not just list the terms; define them and what they mean. Include all key sections and components and explain in your own words.
2) What are the key Critical Path Steps?
3) How do you calculate the Critical Path? Explain with some detail, not just 1-2 sentences.
4) What are parallel tasks in the Critical Path? Explain.