difference between top down and bottom up parsing techniques?

Question

I guess the same logic is applied in both of them, i.e replacing the matched strings with the corresponding non-terminal elements as provided in the production rules.

Why do they categorize LL as top down and LR as bottom-up?

Answer 1

Bottom up parsing:

Bottom-up parsing (also known as shift-reduce parsing) is a strategy for analyzing unknown data relationships that attempts to identify the most fundamental units first, and then to infer higher-order structures from them. It attempts to build trees upward toward the start symbol.

Top-down parsing:

Top-down parsing is a strategy of analyzing unknown data relationships by hypothesizing general parse tree structures and then considering whether the known fundamental structures are compatible with the hypothesis.