Reflect doesn't appear often as a key word on exam questions, but when it does it typically asks you to express how the ideas or applications you've been studying have affected your personal point of view. Reflection is one of the more personal kinds of writing because it invites self-exploration. Of course, taking a personal perspective doesn't mean giving up any connection to outside reality. The idea is to connect your own "take" on the idea with what you've heard in class, studied in the text, or practiced in the lab.
Writing tip: Because reflection is more personal, don't try to write this response without using an "I" point of view. And don't forget to make explicit connections between your personal critical thinking and the idea or concept you've been thinking about.