I think those Jews who were capable and fit to perform manual labour went to concentration camps, whereas those who'd expended their use were sent off to extermination camps, told that they'd be "leaving through the chimneys" as one survivor recalls. Inmates of concentration camps were put to work on various projects, mostly war-related. More broadly though, the term "concentration camp" refers to both the camps where Jews were killed as well as the ones on which they worked; the Nazis used it as a kind of euphemism. So in that sense they're one and the same and you could use the terms interchangeably.
Jews were basically humiliated on these camps, often used for target practice. Women were often disgraced.
I'd advise you to not only mention the Jews in your essay, but also those other groups that were rounded up, such as political prisoners (communists), gypsies, homosexuals and educated Poles.
