I will try to answer this question. When you define a marketing research problem you are trying to reduce the outcome of an answer. The question of course when you speak about "marketing research" is how can I target more customers that I can sell my product to. You are looking for specific answers such as: "What type of soda do all foreign born males between the ages of 25-35 drink?" This is defining the problem. What do you consider foreign born males? What constitutes soda? ETC.
This is important because companies and sales organization attempt to "target" their market instead of taking a shotgun approach. The process is to first make sure any information you obtain is credible and from a reputable organization. Then break down your problem and pick apart any inconsistencies you may see within you research project. Good luck