The main settings are the city of Venice and Portia's home at Belmont, both stands for different aspects of the play. Venice, a rich trading town is represented as a symbol of wealth by Antonio but also as a greedy society where jews had to live in ghettos and had to wear red hat to identify themselves. Belmont is the world of ideal love, it's an idyllic place where lovers come to and where Christians and Jews are brought together, so it's Venice opposite
Love is one of the main themes of the plot, represented in different ways: the love of a friend (Antonio and Bassanio), love for relatives (Portia and his father), romantic love (Lorenzo and Jessica), love for money (for Shylock). Another important theme is the double ways to represent mercy, the Christian ideal from the New Testament which says "turn the other cheek" and the Jew ideal from the Old Testament which, on the contrary, says "an eye for an eye, a tooth for a tooth". Another theme is the appereance and the reality.
Even if in Elizabethan England there were prejudices about Jews, Shakespeare included also different elements about this theme. He emphasises Shylock's humanity and complexity, but his lack of mercy for Antonio doesn't allow to consider him as a completely positive character. At first he's seen as a very human character thanks to his daughter, his friend and the nation he belongs to, but later Shakespeare represents the difference between Christians and Jews, these last ones consider business more important than human relationship. Also Christian characters are presented in ambiguous ways: Bassanio wants to marry Portia because he's in debt, and Christians hates Jews only because they are Jews even if Christians talk about mercy, love and charity.