It's one virulogical theory about the origin of viruses. No one really knows how viruses originated, especially since they aren't technically alive, and depend on living cells to replicate. Living eukaryotic cells make proteins that have to be transported out of the cell, the golgi complex packs the proteins into vacuoles and sends them out the membrane. Those vacuoles sometimes contain rna, and look very much like a type of virus under a microscope. So one theory is that those are the origins of viruses.