What is the difference between memoization and tabulation?

Memoization, or top-down DP, starts from the original problem and recursively breaks it into subproblems, caching results in a hash map or array to avoid recomputation. It only solves subproblems that are actually needed. Tabulation, or bottom-up DP, builds a table starting from the smallest subproblems and iteratively fills in larger ones until reaching the answer. It avoids recursion overhead and stack overflow risk. Both produce the same time complexity.