What does "area of physics or chemistry" mean in a graduate application? On the application form (for Max Planck institute), there is a section which says "Please write a short summary of the area of physics or chemistry you find most interesting".

I am not sure what do they exactly mean by "area of physics or chemistry". Should I write a summary of the general field of my interests i.e. condensed matter physics or about the research topic on which on want to work i.e. phase transitions?
It sounds like you should write about what you want specifically want to study. Anybody can write a page or two about a general branch of either discipline—but that wouldn't help an admissions committee decide if they wanted to hire you or not. A page or two (or some other length, if listed in the question) about your particular research interests would be much more valuable to a committee.