Even days before the exam, everyone knows how overwhelming it may be to be unsure about a concept and its application of it. While you may be perplexed by this concept, someone in your class is almost certainly an expert in the same specific area. Also, it is possible that you may have expertise on another matter that your friend is confused about.
Having said that, conducting study groups is usually beneficial, and why it is very popular among college and university students. Students in these groups can assist one another in internalizing concepts that they are having difficulty with. Even teaching others about a new concept can help you internalize it even more. After all, when the subject matter is interesting, knowledge is better stored in the brain.