Think of it as wire. You can send power through it like electricity to power stuff.(like pistons, torches, and torches). You can find tutorials on it on the minecraft wiki and on YouTube.
Repeater: A repeater resends the signal, but with a delay.
Redstone Torch: Can invert the signal. Also a power source.
Redstone: Wire. It carries signals for 16 blocks.
Piston: Can push blocks.
Sticky Piston: Can push a block, and retract it.
Lantern: When powered sends out as much light as a glowstone block.
Button: Sends out a short burst of signal.
Lever: Sends out an on or off signal.
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