An autotransformer is a single coil of wire wound on a core. The high voltage is applied to the entire coil, and the low voltage is tapped off between one end of the coil and a point near the mid-point of the coil. This can be dangerous, because there is a direct connection between the input and the output.

A proper transformer will have two coils wound on the same core. One coil will have roughly half of the number of turns as the other coil. With the high voltage applied to the bigger coil, the smaller coil will have a smaller voltage available at its terminals. This is a safer system, because the coils have no direct connection between them. They are isolated from each other.

As far as I know, most 'power conditioners' only have surge suppressors in them, to prevent voltage spikes from damaging equipment plugged into their outlets. Isolation transformers with step-up or step-down voltage selection would be quite expensive.