If you had a distribution from a deferred tax account/retirement account, they ask if that is a required minimum distribution (RMD).
Most of the time, (but not all cases) an RMD is for those attaining the age of 70 1/2 and have to take distributions from an IRA, 401k, or other retirement account.
If the distribution you took was in fact a RMD, or part of it was an RMD, then answer Yes. If the withdrawal was not a RMD, then answer no.