Are you speaking of the Medicare Part D prescription drug coverage? I went to a meeting to learn about this for my mother in-law and have never seen so many intelligent, well-educated, but totally confused seniors.
Here is a link to a site for the Council on Aging:
mymedicarematters.org/ It gives a good explanation of things. The Medicare site is helpful, too.
There are so many plans, and it can be so confusing, depending upon what drugs your parent takes. There are good charts available that show the different plans. The advice about visiting the local senior center is excellent, as it is likely your best bet to start. They can be helpful for other Medicare-related questions, as well (and you can generally get in without waiting forever, as with government agencies…)