Hacking describes two kinds of realism. Entity realism Theoretical realism
(28) 3 ingredients to scientific realism, taken from W. Newton Smith
1. ontological ingredient: theories are true or false in relation to the world 2. causal ingredient: theoretical entities, which are real, cause the observed phenomena 3. epistemic ingredient: in principle, our beliefs in such theories and entities are warranted
Hacking's realism about theories is 1 and 3. His realism about entities is not exactly 2 and 3, because he maintains that one need believe in the theories about entities in order to believe in the entities. (potentially pro Parcher).
Hacking also distinguishes between realism-in-general and realism-in-particular. Realism-in-particular concerns specific entities or theories with a certain research program, and over time anti-realism about particulars sometimes give way to realism about that particular. Hacking is mainly concerned with realism-in-general. Broadly construed, science is about theory and experiments, representing and intervening, respectively. Hacking contends science at the level of theory, representing, is hopelessly entangled with metaphysics and the philosophy of language. For Hacking, there will be "no final argument for or against realism at the level of representing" (p. 31). Experimenting, intervening in the world, is our surest warrant for realism and the likeliest defeat of anti-realism.
Hacking, I., 1983, Representing and intervening, Cambridge University Press, Cambridge.