Minecraft wiki entry for Redstone_mechanics, associated text: 1 Redstone Concepts
1.1 Redstone tick
1.2 Redstone components
1.3 Power
1.4 Signal strength
1.5 Signals and pulses
1.6 Activation
1.6.1 Activation behavior
1.6.2 Powered vs. activated
1.6.3 Normal activation rules
1.6.4 Special activation rules
1.7 Redstone block updates