Several things are happening in the exchange between the clown Launcelot Gobbo and his father Gobbo found in 92-103 in Act 2, Scene 2 of Merchant of Venice. While we are limited in space, here are a few things to help understand it better and get you started.
First, we can assume that Launcelot was probably still very young, possibly in his early teens or preteens, when he went into service for Shylock because, as peasants, his family was probably in much need of the income he could produce. We can also assume it may have been several years since his father has last seen Launcelot; hence, when Gobbo exclaims, "Lord, how art thou changed!," it is because he is noting that his son has now grown up to be a man. We know that Gobbo is referring to physical changes based on the earlier lines. As soon as Gobbo understands that it is his son he is speaking to, his first remark is to comment on how full his son's beard has become and compare it to Gobbo's horse's tail.
What happens next in this exchange is that Gobbo asks Launcelot how well he is liking Shylock as his master, leading to Launcelot's next comment, "My master is a very Jew" (97). This line should actually be understood as an insult to Shylock. In these days, Jews were still being judged by certain stereotypes, such as being selfish, greedy money grubbers. Shylock is not only characterized as a selfish, greedy money grubber, he is even characterized as one who is hateful and puts the desire for revenge above all other things, even mercy. Specifically, for Launcelot in this scene, Launcelot is portraying Shylock as a cruel master, even one who does not feed him well, as we see in his lines,"I am famished in his service; you may tell every finger I have with my ribs" (98-99). Lines 98-99 are a very interesting comic device making use of trope, or type of figurative language, called catachresis. A catachresis is an absolutely impossible figure of speech, usually created by mixing grammar. Dr. Wheeler gives us the example, "Joe will kittens when he hears this!" ("Tropes"). Normally, a typical figure of speech used to describe starvation is to say that you can see or feel with your finger every rib in the starving person's body. But, for comic effect, Launcelot has mixed up the expression to say that you can take his ribs and use them to feel every finger he has.
Hence, essentially this passage and scene are all about Launcelot's reasons for wanting to leave Shylock's services; plus the passage and scene are providing another opportunity to further characterize Shylock.