Inputs (sources of current)
-Redstone torch: Acts as an always on source of current.
-Lever: Can be toggled between two positions, always on in one position and always off in the other.
-Button: Produces a "pulse" when pushed that provides current for .9 seconds.
-Wooden Pressure Plate: On when there is enough pressure on it to be activated, it can be activated by throwing a block or item onto it or by a player/mob standing on it.
-Stone Pressure Plate: On when there is enough pressure on it to be activated, requires a mob or player to stand on it to provide enough weight.
-Detector Rail: On very briefly when a minecart passes over it.
Guts (everything in between inputs and outputs)
-Redstone torch: Acts as an inverter and is needed to move power up vertically.
-Blocks: A block can be charged by a redstone current even if it doesn't have wire on it.
-Redstone wire: Carries current up to 15 blocks.
-Redstone Repeater : When a signal is present on the input side it emits a signal out the output side. The signal can only move one way through it so it acts as a diode. It also acts as an extender for the range since wire can only carry the signal for up to 15 blocks. It's also used to built timers and pulse generators. It has a switch on it with 4 positions. Each position adds .1 second of delay to the signal output. So position 4 is .4 seconds delay, position 1 is .1 seconds, etc. You can stack repeaters right next to each other in an array and adjust the switches for precise signal delays. For a 1 second delay for example you would need three repeaters, position 2 (.2 second delay), position 4 (.4 second delay, and another position 4 (.4 second delay). .4 + .4 + .2 = 1 second. It is the only device that does not require the redstone wire to actually be facing the direction of the input side, it just needs to be on the block next to the input side, the same goes for the output. Because of this it makes a useful trigger for powered blocks. I will demonstrate this concept later in the guide. They are also needed to move current down vertically.
Outputs (objects powered or activated by current)
-Redstone Torch: Acts as a light source which can be turned on/off by a redstone current. That's right, a redstone torch can be considered an input, output, or circuit component.
-Wooden Door: Opened/closed by either a redstone current or a player.
-Iron Door: Can only be opened/closed by a redstone current.
-Trapdoor: Think of it as a horizontal wooden door that blocks vertical movement (instead of a normal door which is vertical and blocks horizontal movement).
-Minecart Track: When you make a three way intersection of minecart tracks you can use redstone current to change which two tracks are connected.
-Booster Rail: Slows down minecarts passing over it if it is not powered by a redstone current. If it is powered then it speeds up minecarts passing over it instead.
-Fence/Gate: Gates can be built by stacking fences on top of each other. Gates can be moved up and down by a redstone current.
-Piston: Can push a neighboring block 1 block in any direction. Pushed when exposed to current and retracts when it isn't.
-Sticky Piston: Can push or pull a neighboring block 1 block in any direction. Pushes when exposed to current and pulls when it isn't.
-Noteblock: Can be tuned to a variety of instruments, octaves, and notes. It produces a note when exposed to current. Remember to use repeaters to control the timing of notes in songs.