An SOP or statement of purpose goes by various names in various institutions. Some admissions teams call it an admission essay, while others might call it an applicant statement. It is meant to be a written statement by a prospective student applying to university, college or any graduate school.
A statement of purpose is a personal essay that you, as a student candidate, need to write. It is an important document that is required by the university admission committee to understand better who you are, your learnings and work experiences, and your future career aspirations. It is in your statement of purpose that you will highlight the reasons you have chosen to study at a particular university and a specific course. The statement of purpose should showcase how you will not only benefit from studying this program but also how you plan on using the knowledge you learn in your future career.
So, in summary, your statement of purpose is unique to you. It is a one page essay that explains to the university who you are, why you're applying, why you're a good candidate, and what you want to do with the degree in the future.