Combinatorics is a difficult subject because it encompasses a massive idea. It can be used for simple processes, but it was designed to simplify more complicated calculations of the combinations/permutations of sets of data. Often, combinatorics is difficult to apply because the problem is trying to solve is difficult to understand. On top of that, the full scope of what is considered combinatorics is still undefined. If you are not needing to do a deep dive into combinatorics but are finding yourself need to use the combination formula, there are available combination calculators online.