This is trying to find out what makes you happy, and whether the new employer could provide that for you. If they feel they can't, then they will think twice about hiring you. The sorts of answers you could give are things like "I liked working in a team, I enjoyed taking on big projects and having more responsability".
Of course, these job interview samples of what could be asked in your interview are not extensive, as there are many other questions an employer mght ask to find as much detail about you as possible. The key is to remain positive and always try and give the employer another reason to hire you as each question goes by.