This is a list of all types of prescription drugs covered by an insurance plan.  They are sometimes called drug list.

There are sometimes different tiers to a formulary, and depending on which tier a prescription falls, you will pay a different amount.  If a prescription is not on a formulary, it is not covered, though there are most often alternatives proven to be just as safe and effective at a lower cost.

The drug list do change and are very rarely the same between health insurance companies.