In this case, I’m talking about a virus (or viral gene) that is embedded with the genome of a larger organism, like a human. The human genome contains a huge number of nucleotides, and not all of them get transcribed into RNA or translated into proteins. Our genome is littered with dormant viral genes that would be harmful if expressed. When one of these genes gets turned on by accident (or for whatever reason), RNA and proteins can “leak out” of our genome and start creating pieces of the viral form.
Does that make sense?
If you’re interested in digging into the details of these processes, I suggest getting a copy of my book. I go a lot deeper into this concept and explore how it relates to much bigger ideas.