If you have a Roth IRA, your distributions are taxed differently depending on when you withdraw money, how much you withdraw, and how long your account has been open. In some cases, your reason for withdrawing money also matters. Distribution codes record this information, and indicate whether you owe taxes or penalties on any portion of the distribution.
Code Q in Box 7 of your 1099-R indicates that you took a qualified distribution from your Roth IRA. This means that at the time you withdrew money, your Roth IRA had been open for at least five years, and you were at least 59.5 years old. Alternatively, you can take qualified distributions if you are disabled, or because the original owner died.
Because you took a qualified distribution, you do not owe income taxes or penalties on the amount. If, in the same year, you took a distribution that did not fall into the Code Q category, your trustee should report the information on a separate 1099-R. You may owe taxes on those amounts.