It is like the Flint of Michigan. There is your normal drugs, gangs, violence, etc but what it is mainly is poor and uneducated with a lot of unemployment. Just to give a few comparisons:
Unemployment rate
Stockton:14.20%.
United States average: 6.30%
Income per captia
Stockton $19,906
United States average $$28,051
I dunno about it mainly being about poor and uneducated. Both Stockton and Flint are significantly more violent than the national average, especially Flint. From what I've read the murder rate in both Flint and Detroit is more than twice the worst city in California.
Murder Rate
Stockton: 16.4
Los Angeles: 6.7
Oakland: 19.5
Property Crime Rate
Stockton: 4390
Los Angeles: 2128
Oakland: 5943