Reading this table
The three temperature columns are the conductor's insulation rating, not the ambient temperature. A 90°C-rated conductor is not permitted to run hotter than the equipment it terminates on allows — and most breakers and equipment are listed for 60°C or 75°C. In practice the 75°C column governs most installations, and the 90°C column is used as the starting point for derating rather than as a final ampacity.
The overcurrent cap column
The smallest conductors carry a fixed protection ceiling that is separate from ampacity. It exists because small conductors have little thermal mass and are easily damaged, and it applies regardless of what the temperature columns read. The cited section carries specific exceptions this table does not reproduce.
Aluminum specifics
Aluminum is not listed at 14 AWG. Compared with copper of the same size it carries less current and has higher resistance, so aluminum runs need larger conductors and drop more voltage over the same distance. It also requires terminations listed for aluminum and an antioxidant compound at connections — the corrosion and creep failures aluminum is remembered for are largely termination failures.
Before you use these numbers
Correct for ambient temperature and adjust for the number of current-carrying conductors before sizing anything — see the temperature correction and bundling adjustment tables, or let the ampacity lookup apply both.