If you want to learn more details, here are some helpful, reliable summaries.
5 Key Facts: Straight Talk for Seniors [1]
Questions and Answers about Medicare and Health Care Reform [2]

If you want to learn more details, here are some helpful, reliable summaries.
5 Key Facts: Straight Talk for Seniors [1]
Questions and Answers about Medicare and Health Care Reform [2]
Links
[1] https://mlsed7.n2c.us/sites/default/files/facts.pdf
[2] https://mlsed7.n2c.us/sites/default/files/Questions-and-Answers-on-Medicare-and-Health-Reform.pdf
[3] https://mlsed7.n2c.us/sites/default/files/medicare_advantage.pdf