A 110v transformer conducts electricity through through coils and moves electricity between circuits. When a changing current is applied to the first winding (coil), it creates a changing flux in the core of the transformer which, in turn creates a differing magnetic field in the second winding. When the changing field is applied, a varying voltage occurs in the second winding creating a mutual induction effect. An electric current will flow through the second winding and then an engergy transfer occurs when a load is connected to the second winding. Engergy gets transferred via the primary circuit to the load.
Transformers can be found in varying sizes from something as small as a dime to something much larger and weighing many tons. The largest ones are typically found in the power industry. 110v and 220v transformers are found in consumer appliances and smaller industrial components and share common electronic characterstics. There are many types to consider.
Voltage Converters are some of the most common types and can be either step-up or step-down in nature. The step-up converters allow an appliance rated for a lower voltage to be used with higher voltage mains. This is a common travel scenario when traveling from the Americas to Europe or Asia. The opposite is also true. Travelers from Europs often need step-up transformers to power their appliances when going from a location where 220v is the norm to one where 110v is more common. In addition, most transformers that are built for consumer appliances have voltage regulation and or surge suppression built-in as a capability. These are often more expensive, but may be worth the price in the event of an electrical storm or just when the appliance is vulnerable to significant changes in current.
On the industrial side, transformers are critical to transferring energy over long distances. This is only possible because the transformers in between can convert the higher voltage necessary for efficient long distance travel down to a voltage that is useable by business and consumers.
For audio electronics, signal and audio transformers are used with amplifiers and to equalize their input to devices such as a microphone or phonograph. This type of transformer also allows phone conversations to occur asynchronously over a single pair of wires.
Overall, the transformer, while a simple electronic component in principle, is critical to the operation of modern cities, homes and electronics. Efficient transmission and usage of electricity would not be possible without the transformer.