A redstone torch is a constant power source and a signal inverter: it outputs power level 15 when lit and switches off when its attachment block gets strong power.
Bedrock Edition · Block dictionary
Redstone Torch — spec
Power output
15 (strong), when lit
Placement
Floor or wall; never hanging from a ceiling
Delay
2 game ticks (1 redstone tick) to flip
Powers above
Strongly powers the block directly above it
Bedrock rule
Only STRONG power on its block turns it off; weak dust power is absorbed
