stockfish - Why do Engines show a fraction for the Depth and Current Node values? - Chess Stack Exchange

Forgive me if this has been asked elsewhere, but I've both Googled and searched here at CSE and cannot find an answer. When I'm using an Engine for analysis (in this case, Stockfish 15), I've noticed

Stockfish: In-Depth look at a chess engine (1)

Stockfish will analyze a chess position through to (for example) depth 45 and announce a mate in 10. When it reaches depth 56 it finds an improvement, to mate in 9. Why

Stockfish will analyze a chess position through to (for example) depth 45 and announce a mate in 10. When it reaches depth 56 it finds an improvement, to mate in 9. Why does it need such deep analysis to find such short mates? - Quora

engines - What is the deepest Stockfish evaluation of the standard initial position that has ever been done? - Chess Stack Exchange

Stockfish - Chessprogramming wiki

PDF) Statistical analysis of chess games: space control and tipping points

What is the algorithm behind Stockfish, the chess engine? - Quora

stockfish - Why do Engines show a fraction for the Depth and Current Node values? - Chess Stack Exchange

engines - Is Houdini 6 a Stockfish clone? - Chess Stack Exchange