What does this excerpt from act 1 of romeo and juliet reveal about the montague-capulet feud?

abraham: do you bite your thumb at us, sir?
sampson: i do bite my thumb, sir.
abraham: do you bite your thumb at us, sir?
sampson: (aside to gregory) is the law of our side, if i say ay?
gregory: no.
sampson: no, sir, i do not bite my thumb at you, sir, but i bite my thumb, sir.
gregory: do you quarrel, sir?
abraham: quarrel sir! no, sir.
sampson: if you do, sir, i am for you: i serve as good a man as you.
abraham: no better.
sampson: well, sir.
gregory: say 'better: ' here comes one of my master's kinsmen.
sampson: yes, better, sir.
abraham: you lie.
sampson: draw, if you be men. gregory, remember thy swashing blow.