What does filtered mean?

filter4dL-グルタミン 200 mM, solution, sterile-filtered, BioXtra, suitable for cell culture; CAS Number: 56-85-9; EC Number: 200-292-1; Synonyms: Glavamin,Levoglutamide at Sma-AldrichTable-top filters can remove contaminants from tap water – but are they really necessary, and could they cause unintentional harm? If she can help it, Shima Chin-See