Zero, or no mutation difference at HVR1 and HVR2 regions of mtDNA means that the mtDNA profile from the HVR1 and HVR2 regions of your mtDNA is a perfect match to the HVR1 and HVR2 profiles of another person. This indicates that you may possibly be descendents of the same Maternal line.
SNP markers in mtDNA mutate at a very slow rate of once every few thousand years. This is why a perfect match in your mtDNA profile suggests that you likely belong to the same maternal lineage. However, this does not necessarily indicate that you are close relatives, because a match will detect all relatives that are in your direct Maternal line within many generations.
Any individual who does not match your mtDNA is definitely not related to you along your maternal lineage. These findings can be further refined by comparing the coding regions.