What is semi-conservative replication of DNA? And why is it important?

Semi-conservative DNA replication involves splitting open the parent cells DNA duplex and exposing both strands. Now these strands are accessible to replication machinery to act as a template, so that the sequence can be 'read' and a daughter strand synthesised that is complementary to each parent strand. This will produce two DNA duplexes which have one parent strand and one daughter strand. The semi-conservative mechanism minimises errors in DNA replication, because the template gives DNA polymerase something accurate to copy from. This is very important because cells want to minimise errors in replication when dividing, so that mutations (such as incorrect bases, deletions, insertions) are not brought into the genome. Mutations in genes can cause proteins to become non-functional and lead to disease, including cancer.