The creation of the ghettos?

I'm not sure what you are asking here. During World War II, the Nazis established more than 400 ghettos in order to isolate Jews from the non-Jewish population.

The word "ghetto" from Venice in 1516 and firstly was used to name Jewish area in Venice. 300 years later this term was extended to name all urban quarters inhabited by other minority groups. The have been quite a big number of ghettos all over the world, if you look thoroughly into history you will find that there were Jewish Shanghai ghetto, American ghetto, Moroccan and Europe ghetto. There is no clear evidence why people decided to live in such a way, however it partly explained by language, etnicity and culture background similarity.
Hope it helped but if you need more information click the link in a source, because the resource has the experts in history with an amazingly deep knowledge and I an sure they will answer all your questions