Redstone Signals and Components

Redstone dust acts as wire. A fresh signal starts at strength 15 and loses 1 strength for every block of dust it crosses, hitting 0, and going dark, after 15 blocks — that's the hard range limit for a single unbroken run of dust. A redstone torch is both a power source, outputting strength 15, and an inverter: it stays lit and outputs power whenever the block it's attached to is unpowered, and switches off the moment that block receives power from somewhere else, flipping the signal.

A repeater sits inline with dust and boosts whatever signal reaches its back straight back up to full strength 15, letting a wire keep going well past 15 blocks. It also adds a small delay, from 1 up to 4 redstone ticks (0.1 to 0.4 seconds), adjustable by right-clicking it, and only lets signal flow in the one direction it's facing. A comparator looks similar but works differently: instead of boosting to a fixed 15, it passes through the same strength it receives at its back, and can compare or subtract a second signal fed into its side — it's also the one component that can read how full a container like a chest or hopper is and turn that into a redstone signal strength.

Put together, these pieces cover the three jobs every redstone build needs: something to make a signal (a lever, button, pressure plate, or redstone torch), something to move it (dust, with repeaters where distance demands it), and something to act on it (a piston, door, or redstone lamp). A repeater powered from its side by another powered repeater or comparator "locks," freezing its output at whatever it currently is until that side power goes away — a detail that trips up plenty of first builds that seem to randomly stop responding.