Use the example of the question "Is jogging good for pigs?" to help you understand what constitutes a "concept".
Clearly, "jogging" is a concept. Equally clearly, "pigs" is the second concept of your search strategy.
The difficulty is whether or not to include the term "good" as a third concept. If you do, you will need to have an extremely large string of terms that include terms such as "bad" (the negative side of "good"), as well as terms that will identify those articles in the database that indicate that jogging has "no effect" at all on pigs. To do so is extremely difficult.
It is therefore better in terms of your search strategy to omit this concept from the original search, as it is a subjective and qualitative evaluation that will actually be determined best from your research or experimental data. You should include in your literature search all articles that you can find which prove that jogging is good for pigs; all articles that you can find which prove that jogging is bad for pigs; and all articles that you can find which prove that jogging has no effect on pigs. Your research or clinical examination and tests will determine your hypothesis (problem statement). Your literature search will not necessarily do so. Your literature search will however show that you have read widely around your topic and that you can argue the merits and demerits of all issues concerned with your topic.
The tutorial below will assist you to design a better strategy, and thus perform a better search. You will need to master this before moving on to evidence-based searching.