Does the employer mean the degree of automation? Or a test object? Or isolation of components?
And you can keep asking, which is a good thing in my opinion. You obviously want to clarify what they mean by this broad question. That might help you see how they approach testing, and it will help them see what you have experience with.
what does the employer want to hear?
Obviously that's context dependent. In general terms, they want to find out more about you so they can figure out if you help them in their business.
You also asked in the comment section:
I'm trying to get inside HR's head and figure out what they want to know. Are they trying to figure out if I remember testing theory and classification? Or are they really interested in my experience? But then why not to ask what projects I worked on?
Aha, so this is actually an answer for HR people... That might be tricky, because in my experience they usually don't know much about the actual job. Having said that, they might look for answers that fit some ISTQB material they happened to read somewhere. In a better-looking scenario, they have a job description somewhere near and they look for keywords in your answer and in the job description, if they match, further you go. The best scenario is they pass/discuss your answers to/with someone with technical/testing skills and let them decide. In my experience, HR people often pair up with technical people during the hiring process, so they get regular help from technical people regarding technical questions and answers.
All in all, it's all speculation here. I'd pretty much answer with what you keep hinting at here, no need to sugar-coat your answers just because you assume something.