Discuss the differences between the various types of Offenders locked up in county jail or prison?Why do they commit specific types of crimes?
County jails are quite different places than full-fledged prisons. In most states, the maximum a person can be sentenced to at a jail is two years. For crimes that have longer sentences than that, they are sent to prisons, which are considered maximum security most times. Jails are usually minimum or medium security. You can find violent offenders in both types of lockup, though the more serious or habitual offenders usually end up in prison.
First time drug offenders, or those charged with misdemeanor possession, or non-violent burglary charges are usually sent to jail, while murderers, sex offenders and more serious criminals end up in prison. You can also find very violent criminals in jail while awaiting trial, that is, when they have not yet been convicted. They are usually segregated from the mainstream jail population.
As for the second part of your question, there are a hundred possible reasons why criminals do what they do. Sometimes there seems to be no reason at all. Criminologists have theories about background, education, even genetics and poverty, but it's very difficult to prove without doubt what motivated each individual criminal.