They’re basically looking for the kind of stuff you’re only going to know after you’ve been established in your career for awhile. Do you want to work for big companies or small companies? Do you want to lead a team? Do you prefer greenfield development or maintenance? What industries would you like to develop software for? Law, medicine, finance? Unmanned drone farming?
Basically, that question is an invitation for you to set yourself apart from everyone else just looking for a job. You can put pretty much anything there. Expect to be asked about it in the interview, so be prepared to elaborate.