- DP is a general problem solving approach

- DP is not limited to any particular implementation detail (like my parent poster attempts with "it's just a simple cache mechanism")

- DP is not a "trick" that you can learn and then solve any DP problem

If we have a DP solution, we can write it in many ways. We can write it top-down with recursion and memoization, or we can write it bottom-up without memoization. Whether we use memoization in our solution or not is a minor implementation detail. Both solutions are DP. Other posters seem to make a distinction between these two solutions as if they are entirely different and as if the recursive solution is not dp - this is also incorrect. The challenge in DP tasks is about improving time complexity by recognizing repeated sub calculations.