Distillation is simply a separation process By boiling point. Take an original sample of water. It contains h2o and dissolved minerals and some trace elements. Now boil that sample but do not exceed the correct temp (212f or 100c). Now your sample is in a vapor phase, gas/steam. The gas/steam is purely h20 w/o trace elements Nd minerals. The steam is condensed (cooled) and the pure liquid h2o collects in a separate rez and the minerals n compounds are left behind.