Hi kmark,
An adjustable bed is usually a “stand alone” product that has an articulating surface so that the upper and lower parts of the mattress can be raised or lowered into different positions. Many of them also have many other features such as massage that you can feel under the mattress. It would generally be used instead of a platform bed or a bedframe and foundation (or box spring) combination.
Of course you could also remove the slats and center beam in your bedframe and use the adjustable bed inside the side rails and head and footboard of your bedframe so its heavier weight would be supported directly on the floor.
There are also some that can be used without legs directly on the slats of your bedframe as long as the bedframe is strong enough to support the weight of the adjustable bed, your mattress, and the people sleeping on it. A few examples of these are here and the Ergomotion adjustables can all be used on a platform and the Leggett & Platt S-Cape with the DC motor and the Reverie 5D (Deluxe) can apparently also be used directly on a platform bed. There may be others as well that I haven’t asked about.
There is more about adjustable beds in post #3 here and the adjustable bed thread that it links to.
Phoenix