Shylock was a Jew who practised usury, that is lending money at highly exaggerated interest rates to "get rich quick."
In many countries in Europe, Jews were already forbidden to own land, so quite naturally they turned to trade to earn their living instead. Then when they becane prosperous at that, both prejudice and jealousy over their newly found wealth ostracized them as a marginalized group even more.
Shylock is a good example of a stereotype or stock character: he looks like and behaves as one would expect, according to the mold into which he has been cast. A Jew is first and foremost penny-pinching, right? - and this is the primary trait which comes through in his character profile. There is little or no room left over for personalized expression, nor is there much surprise in store from him, either. The character of Shylock also serves as a foil for Portia since his vices put into value her virtues by contrast:
Shylock was a Jewish merchant and money-lender. There is occasional criticism of this play as being anti-Semitic, because several characters refer to Shylock in negative terms and the pejorative 'Jew' is paraded frequently. But Shylock himself is not usually portrayed as a sympathetic character. He is cruel, calculating and heartless. He does gain some sympathy in his exchanges with his daughter, who he thinks highly of. He is hated in Venice because of his usurious ending practices (charging high interest on loans) and for his cold-blooded acts of revenge against those who have wronged him, as when he draws up the 'pound of flesh' agreement that will allow him to murder Antonio.
In Shakespeare's comedy "The Merchant of Venice," the character of Shylock is a Jewish moneylender who lends money to Antonio, a Christian requiring a bond of "a pound of Antonio's flesh." When Antonio goes bankrupt, Antonio defaults on the loan, and Shylock demands his pound of flesh in a court of law, as revenge for Antonio having previously insulted him. At the same time, Shylock's daughter Jessica, elopes with Antonio's friend Lorenzo and becomes a Christian, further adding to Shylock's anger and resentment.
Issues that dealt with Jews and Judaism were very controversial during the Renaissance Period because Edward I had them expelled in 1290 but Oliver Cromwell allowed Jews to return in 1656. Jews had to practice Judaism in secret between those years.
In one of the most famous soliloquies in the English language, Shylock explains that Jews are just like "everyone else" when he says:
I am a Jew. Hath not a Jew eyes? Hath not a Jew hands,
organs, dimensions, senses, affections, passions; fed with the same
food, hurt with the same weapons, subject to the same diseases,
heal'd by the same means, warm'd and cool'd by the same winter
and summer, as a Christian is? If you prick us, do we not bleed? If
you tickle us, do we not laugh? If you poison us, do we not die?
And if you wrong us, do we not revenge? If we are like you in the
rest, we will resemble you in that. (iii.1.58-68)