Part A covers inpatient hospital stays, care in a skilled nursing facility, hospice care, and some home health care.
Most of the time Part A doesn't cost you anything in terms of monthly premium as long as you have paid 40 quarters in the the Medicare system through you taxes while you were working.
If you do end up needing to use your benefits, there is a large deductible that needs to be met before Part A starts paying benefits, but then you will be covered for the 1st 60 days after before you start to realize copays and coinsurance.