Swift uses exaggeration (also called overstatement or hyperbole) in order to draw attention to the piteous plight of the poor Irish tenant farmers. The wealthy English had purchased much of the land in Ireland and began to charge higher and higher rents, so that many tenant farmers were forced to give over all they had just to stay on the land they worked, with no money left over for food or clothes or other basic necessities for their families. Many women and children, then, were reduced to begging. Swift's narrator says, of eating Irish babies (his solution to the problem of begging):

I grant this food will be somewhat dear, and therefore very proper for landlords, who, as they have already devoured most of the parents, seem to have the best title to the children.

Now, the wealthy English landowners have not actually "devoured" their Irish tenants, and this is an example of exaggeration because they have, in a way, figuratively devoured them: they have eaten up their lands and means of livelihood, and the poor Irish seem to grow leaner and leaner while the English grow fatter. The English grow richer while the hardworking Irish grow poorer. This example of exaggeration helps us to understand that Swift wants us to sympathize with the Irish and reject the narrator’s (not-so-modest) proposal. It is through the use of rhetorical devices like this that Swift creates his satire.

Your original question had to be edited as you are only allowed to ask one question, not multiple questions. Please remember to follow the rules of enotes in future.

Exaggeration, or hyperbole as it is also known, is evident throughout this masterful essay in the way that Swift repeatedly exaggerates his position and ideas to make himself appear more monstrous than he actually is. There are numerous examples of this, but one of my favourite parts of the essay where this is shown is when Swift finally reaches the content of his "modest proposal":

I have been assured by a very knowing American of my acquaintance in London, that a young healthy child well nursed is at a year old a most delicious, nourishing, and wholesome food, whether stewed, roasted, baked, or boiled, and I make no doubt that it will equally serve in a fricassee, or ragout.

Note how the long list of possible ways a child can be served is a perfect example of exaggeration. Swift could have just stopped his sentence at "wholesome food." However, by continuing the sentence and by listing the various ways of cooking a child, he makes himself out to be a kind of food connoiseur, which exaggerates his own monstrous proposal when we remember that he is not talking about beef, but about starving children in Ireland. This of course relates to the key element of satire in this incredible essay: Swift makes himself out to be a monster to expose the monstrous attitudes and behaviour in others.