When you refer to a “problem”, I assume you are talking about research? A good research problem should be very specific, measureable and realistic. You will also need to make sure you have enough time to research the problem.
You will usually identify a problem before conducting a research project, and if your problem isn’t identified correctly, you won’t be able to move on to the part where you start collecting the date.
When we talk about a problem being specific, we mean that you need to be able to state the problem in one, simple sentence. If you need more than this, it will likely be too complex.
A problem needs to be measureable in order for you to be able to collect the data to confirm or disprove your hypothesis. A problem needs to be realistic in terms of the resources you have to conduct the research.