During job interviews, employers will try to gather as much information about you as possible, mostly through perfectly legal questioning, but sometimes through simple yet very illegal questions. 
It's up to the interviewee to recognize these questions for what they are.
Any questions that reveal your age, race, national origin, gender, religion, marital status and sexual orientation are off-limits.
"State and federal laws make discrimination based on certain protected categories, such as national origin, citizenship, age, marital status, disabilities, arrest and conviction record, military discharge status, race, gender, or pregnancy status, illegal. 
Any question that asks a candidate to reveal information about such topics without the question having a job related basis will violate the various state and federal discrimination laws," Lori Adelson, a labor and employment attorney and partner with law firm Arnstein & Lehr, tells Business Insider.
"However, if the employer states questions so that they directly relate to specific occupational qualifications, then the questions may be legitimate. Clearly, the intent behind the question needs to be examined."
If you are asked any inappropriate questions, Adelson advises not to lie, but, instead, politely decline to answer.
"Could they not give you a job because of that? Sure. But if they do, they would be doing exactly what they're not supposed to do."
We compiled the following illegal interview questions that are often mistaken as appropriate from Adelson and Joan K. Ustin & Associates, a consultant firm specializing in human resources and organization development.