Your assumption is correct Judythe.

If we want to get down to the really bare, bare basics of a toaster, toaster oven, electric range, electric over, whatever... you're applying line voltage across a heating element that has a high enough resistance to not appear as a short circuit. The heating element (in a toaster, often it is a type of "nichrome" wire or ribbon) turns all the power consumed into heat.

Most all of these heating elements reach their "full cooking power" when they're effectively directly connected to the power - ie, imagine a direct connection from one prong in the outlet to one end of the wire/ribbon in the toaster, then the other prong in the outlet being connected to the other end of the wire/ribbon.

All the cooking/heat controls do in all of these things is either 1) restrict the flow of current to be something less than 100%, or 2) turn the wire/ribbon on/off on a periodic basis. That's it, those are the only two things they do to control the temperature to be something less than 100% or more than 0%.