I have to write an essay on career goals. I am applying for a Master's program. Do I start from the basic as to why I chose the subject and how and what do I intend to do after the master's immediately and in the long run? Or do I just start from what I will do post doing master's from my target university? What are the essential points that I should include?
(Please note that there is not a single, universally applicable answer to this question. So grab a large grain of salt...)
Usually the selection committee will be looking to see if, within the department's discipline, the topics that interest you align with the research goals of their faculty. At the next level they will be looking to see if you write about the discipline with any depth of knowledge, and with any passion.
Beyond that, there are some "strategies" you could adopt while writing your letter. I am not advocating that you adopt any of these, I am just offering some alternatives to consider before you start writing:
You could go the route of digging through the faculty's research, and writing a targeted letter, basically applying to a specific faculty member -- but be careful. Going that route it is easy to start drifting away from what you in the long term might actually be interested in achieving. Remember though, that challenging your intellectual abilities and the image you may hold of yourself as an academic are part of graduate school. So delving into a topic outside your core interests can be a part of your growth as a [insert discipline specialist title].
At the other end of the spectrum, be personal. Write about your passions for the discipline, and don't be afraid to wax poetic. If your academic record is very strong, use the letter as an opportunity to reveal how your personal relationships with other researchers and the research community have stoked your interests. Take this opportunity to speak to any initiatives you've taken to reach a goal (one that could be framed as a "research goal").
Hope this helps!