What does the term "Semi-conservative" mean in relation to DNA?

DNA is a double stranded helix. During DNA replication, the strands are separated from each other (using an enzyme called DNA helicase). The unzipped DNA strands then utilize another enzyme, known as DNA Polymerase, to attach a newly formed DNA strand to the original strands. Therefore, one strand is conserved and one strand is newly synthesized. There was originally one double stranded DNA helix, now there are two double stranded DNA helix.