The distinction is explained two paragraphs above the quote:
"She argues that while the epistemic motivation for doing experiments on C. elegans might be quite far-reaching, the proper epistemic target for any such experiment is the worm itself. In a simulation, according to Peschard, however, the epistemic target is never the digital computer itself. Thus, simulation is distinct from experiment, according to her, in that its epistemic target (as opposed to merely its epistemic motivation) is distinct from the object being manipulated."
This is a more sophisticated version of the distinction between simulations and experiments offered by Gilbert and Troitzsch, which came under heavy criticism:
“major difference is that while in an experiment, one is controlling the actual object of interest (for example, in a chemistry experiment, the chemicals under investigation), in a simulation one is experimenting with a model rather than the phenomenon itself.”
The problem with this view is that the "actual object of interest" in experiments is typically a theoretical abstraction, "energy", "structure", etc., which can not itself be subject to "controlling". And instantiations of abstractions are "controlled" in both simulations and experiments. Peschard replaces the crude idea that experiments give us "access" to the "world itself" as opposed to "made up" simulations with a more nuanced view that experiments are primarily about their epistemic targets and only secondarily about inferences to the behavior of other systems, whereas in simulations the balance tilts the other way.