What's the description of the series code SM.POP.TOTL for Aruba?
Aruba is the name of the country where ShortName = 'Aruba'
SELECT T2.Description FROM Country AS T1 INNER JOIN CountryNotes AS T2 ON T1.CountryCode = T2.Countrycode WHERE T1.ShortName = 'Aruba' AND T2.Seriescode = 'SM.POP.TOTL'