When President Monroe toured the country for the first time at the beginning of his presidency (in the summer of 1817), in order to assess existing fortifications in the Northern States, but also to get in contact with an ample representation of Americans - no other President before him met as many people as he did - he was warmly received. He had a very affable and likeable personality, and everywhere he went, from Maine to Boston, and from Detroit to Washington D.C., he received a fond and enthusiastic reception. It was, in fact, during Monroe's visit to New England, that a journalist coined the expression "Era of Good Feelings," a phrase that has come to represent the years that spanned Monroe's presidency.
To begin with, a political machine is an organization in which an organization gains support via promising rewards to those who keep them in power. It's designed to keep a particular group in power by promising favors. Typically, immigrants who first arrived here were impoverished, so political machines became so successful because they would promise to set immigrants up with homes or jobs or food so long as they had their vote.
So in short:
Who: Organizations whose main goals were getting and keeping power.
What: They essentially bribed immigrants for their votes.
Why: Political Machines did this to stay in power.
They were called the okies