HSA distributions are funds taken out of your HSA that should be used for qualified medical expenses (that would be considered a normal distribution). The IRS requires you to prepare Form 8889 and attach it to your tax return when you take a distribution from an HSA. However, if your 1099-SA indicates you did not use the distribution for qualified medical expenses, you will pay income tax on the portion you used for unqualified expenses.
HSA contributions are funds put into the HSA account to be used for future medical expense distributions. There are limits as to the dollar amount of contributions that can be made into an HSA account each year. These limits for 2017 are $3,400 for self only plans and $6,750 for family plans.