All types of fiction arguably invite their audience to explore real ideas, issues, or possibilities in an otherwise imaginary setting, or using what is understood about reality to mentally construct something similar to reality, though still distinct from it.
Realistic fiction typically involves a story whose basic setting (time and location in the world) is real and whose events could feasibly happen in a real-world setting; non-realistic fiction involves a story where the opposite is the case, often being set in an entirely imaginary universe, an alternative history of the world other than that currently understood as true, or some other non-existent location or time-period, sometimes even presenting impossible technology or a defiance of the currently understood laws of nature.