Essays / SOP question confusion: explanation of your proposed field of study [3]

I am confused about a question that says' " GIve a detailed explanation of your proposed field of study and your specific area of interest"

Does this question wants the explanation why I chose XXX field of study? or What XXX field of study is about or mean?

Your response would be greatly appreciated.

Essays / PhD Social work program - what kind of essay they require? [4]

I am applying to five Phd schools in social work program but confused about writing an essay. I can;t understand what kind of essay they require as they name it different. They state it as

1.
A statement of interest demonstrating commitment to advanced
study in the field.

2. Calgery
educational goals and career expectations, and the research problem to be investigated thought the doctoral thesis; and,

3.Toronto
Study and Research Proposal: 10 pgs.

4. study plan

I am going to include my research proposal along with an essaybut can't figure out if all these essays demand same content or different. Could you plz help me out as I'm running out of time.

thanks