Primarily, transformers have impacted society in that they convert electricity so it is suitable for use in the home by domestic consumers. Transformers allow for the safe distribution of AC electricity in urban and suburban areas, as well as allowing AC to be transmitted over large distances without significant power loss.
As a result, transformers, along with generators, have provided a better quality of life for society because consumers are able to use electricity to make tasks more efficient, and for the use of luxury items.
That's all I can conjure off the top of my head. Check your textbook. It might have some useful information. Or try your library for different textbooks. You could also look at some of the Physics resources on boredofstudies.org. Try searching "bob emery" in Google as well.
As for the second part, I can't exactly just give you information about it because the information is supposed to be from secondary sources, and I presume the source needs to be referenced thoroughly in your bibliography. But I can give you a quick summary:
Basically, the transformer steps the voltage of the electricity up or down depending on the circumstances. Voltage is stepped up if the electricity needs to be transmitted over large distances from the power station to local substations to minimise power loss. There will be transformers at the power station that do this. It is then stepped down using transformers at the substation to homes so that the electricity is safe for domestic use.
Also, smaller transformers are used in small appliances like hair-dryers, otherwise it could destroy components in the appliance.