How is retrovirus replication different from normal DNA viruses?
Retroviruses package a copy of their genome as RNA, so they need to make it into DNA before they can insert it into the host genome
Retroviruses have RNA genomes, and RNA can't get integrated into Eukaryotic genomes (which are DNA), so the virus has to also package an enzyme called Reverse Transcriptase, and this enzyme makes a DNA copy of the genome. This copy of the genome can then get inserted into the host genome.
A DNA virus doesn't need this reverse transcriptase step.
Reverse transcriptase is extremely important for molecular biology, since it allows us to make RNA into DNA...and so we can make mRNA (which are unstable) into cDNA.