Note the answers of William to the comments and questions of Touchstone. What is this purpose? What contrast is shown?

As Duke Frederick’s fool, Touchstone longs for their life at court and mocks everything and everyone he encounters in the Forest of Arden. His character serves to remind the audience of the equally foolish conventions of court life and of the romantic idyllic rustic escape. However, once he meets the country “wench” Audrey, his opinion of the forest begins to change and the audience sees the Romantic in him emerge. In Act V, Scene 1, Touchstone is courting Audrey when her previous suitor, the rustic William, enters. In an aside, Touchstone refers to the other man as also being a fool, and notes that he will not be able to resist making fun of him.
As Touchstone asks apparently simple questions, and William answers them succinctly, Touchstone builds up ammunition to show that William is foolish and unworthy of Audrey. He does this in the style of a lawyer assembling a legal argument, culminating with the assertion that he, not William, should marry Audrey. William's plain answers affirm that he does not understand what Touchstone is up to, and is not a man of words.

TOUCHSTONE: . . . You do love this maid?
WILLIAM: I do, sir.
TOUCHSTONE: . . . Art thou learned?
WILLIAM: No, sir.
TOUCHSTONE: Then learn this of me: to have, is to have; for it is a figure in rhetoric that drink, being poured out of a cup into a glass, by filling the one doth empty the other; for all your writers do consent that ipse is he: now, you are not ipse, for I am he.
WILLIAM: Which he, sir?
TOUCHSTONE: He, sir, that must marry this woman.

Rather than simply tell William to get lost, the fool continues with an elaborate speech, picking up steam and still mocking William, as he pretends that even plain English words need explaining. While he certainly must know that he is not very scary, he threatens to kill William—not once and in just one way, but 350 different ways, and tells him to “tremble and depart.”

TOUCHSTONE: . . . Therefore, you clown, abandon,—which is in the vulgar leave,—the society,—which in the boorish is company,—of this female,—which in the common is woman; which together is, abandon the society of this female, or, clown, thou perishest; or, to thy better understanding, diest; or, to wit I kill thee, make thee away, translate thy life into death, thy liberty into bondage: I will deal in poison with thee, or in bastinado, or in steel; I will bandy with thee in faction; I will o'errun thee with policy; I will kill thee a hundred and fifty ways: therefore tremble and depart.

Audrey, when he finishes, simply adds “Do, good William.” It is clear that she has thrown over her local suitor for the smooth-talking fool.
http://shakespeare.mit.edu/asyoulikeit/asyoulikeit.5.1.html