It's anti-silo. Instead of group A building software in isolation and then tossing it over wall to group B to deploy. Those groups merge, cross-pollinate or at least communicate frequently. So, the group building software is away of the needs/issues of the group deploying/running the software and vice versa.
extend to other groups functions (QA, maintenance, sales).
It doesn't matter if one person does a bit of each role or if there are persons for each role. As long as the work closely together.