It requires a high degree of initiative, independence, and self-discipline. For people who are interested in ideas, creative thinking, and problem solving, the Ph.D. offers the greatest challenge and the greatest rewards. The traditional career for recipients of the Ph.D. is college teaching. But in many fields, particularly in science, people with doctoral degrees find employment with corporations where research and development of new products or services are important, or with government agencies where the skill to analyze large amounts of complex data is essential. The master's degree generally serves as certification of skill in an academic or practical area.
People also use study for the master's as a way to determine interest in pursuing higher degrees.
The doctoral degree requires four to six years of intensive study and research. As for what one does with a Ph.D., the expectation is that the doctorate will become a teacher and producer of knowledge in a particular field. You are responsible for supplying admissions committees with each of these components. Grades Grades are not the only predictor of success in graduate school, so do not be dismayed if yours are not stellar. There are minimum cutoffs in most cases, however, and you need to learn what those are for the programs to which you apply.