Hi there, this article will explain the basics of what each redstone component does in Minecraft. I'm not a redstone expert but know enough to explain the basics so without further ado, here's each redstone component explained, somewhat simply:
Signal - the redstone pulse or state, is it on, off and what strength
Signal Strength - the current strength of the redstone pulse, from 0-15 blocks away
Tick - Minecraft's time unit, 1/20th of a second
Repeaters are a vital component in redstone, they take a signal and amplify it back to 15 no matter what. They also add a delay from 1-4 ticks to the pulse by right clicking it to set the delay. Repeaters are how you make redstone stretch more than 15 blocks and still work.
Comparators, the infamously complicated redstone component, well what do they do? Its actually simple, they have a few functions but the main ones are as follows:
Reading Block State - Comparators can read the state of certain blocks such as chests or item frames, for chests and other containers they can read and output a signal strength depending on the fullness of the container. And for item frames the rotation of the item frame. There are many others such as lecterns but they all follow the same idea.
Signal Strength Comparing - Comparators can also "compare" signal strength, by having a redstone signal into the back and side of the comparator, the signal can be compared. If the comparator's input behind has a signal strength greater than or equal to the signal strength of the side one, it outputs the back signal, otherwise no signal.
Subtracting Signals - Finally, comparators can subtract the side signal from the back one by toggling the redstone torch on the comparator to on, putting it in subtraction mode. In this state the side signal is subtracted from the back one and outputed from the front. If the result is 0 or negative, no signal is outputed.
See, not so complicated after all, just some basic math.
Redstone inputs include:
Levers - When toggled on output a signal of 15, when off no signal
Buttons - When pressed output a signal of 15 for a few seconds then turn off, stone ones are for less time
Targets - Outputs a signal when shot by a projectile
Pressure Plate - Outputs a signal when stepped on
Weighted Pressure Plates - Outputs a variable signal based on how many entities are standing on it
Tripwire Hook - Outputs a signal when its string is crossed
Trapped Chest - Outputs a signal when opened
Daylight Detectors - Outputs a signal based on time of day, right click to change to time based on night
Observers are simple, they simply output a signal out the back of them when the block in front of them (the face side) is updated, placed or broken. Incredibly useful
Sculk sensors output a signal when they detect a vibration or sound, a vibration can be many things so I will link the Minecraft wiki's list here:
https://minecraft.wiki/w/Sculk_Sensor#Vibration_frequencies
Sculk sensors can also be converted to calibrated sculk sensors which will let them be set to listen to a specific vibration.
Hoppers are one of the most important redstone components, they transport items in the direction they are facing. They can suck up items dropped on top of them and will move items in their inventory in the direction they are facing. They also can insert items into other containers, including other hoppers to create a transport chain of items. Hoppers can be toggled off by giving them a redstone signal, when off they will stop transporting items. Hoppers update once per tick so if speed is required, use something better like flowing water.
Dispensers and droppers are similar, the difference being dispensers can use certain items and droppers will always drop the item. Both will dispense or drop an item randomly from their inventory when activated by a signal. Dispensers as stated can "use" certain items as if a player did it, these include:
Dispensers can also put armor onto players and entities when they stand next to it.
Pistons move blocks when activated. They will extend on a pulse and push whatever block is in front of them forward one block. If they are sticky they will also bring that block back when they retract. If not the block stays in its new state.
Note blocks will play a sound, set by right clicking it until you get the right note, when activated. This sound also depends on the block under the note block, check the wiki for which block does what. If a mob head is above the note block the note block will play that mob's sound.
Crafters are complicated so I will try to make this as easy as possible. Crafters will auto craft whatever items are in their inventory, in whatever order they are in when activated by a signal. They will then output this item out the front of the crafter. By opening the crafter GUI with right click, certain slots can be disabled to ensure it crafts the right thing. Items must be added in the order of the recipe slots, so to craft stairs, you would disable the unused slots in the crafter and then fill the crafter with the block using a hopper, since order doesn't matter for this recipe. Then when the crafter receives a signal it will spit out the stairs.
For a more complex recipe such as a compass, you would disable the corner slots, then input the iron first, then another iron, then the redstone and then the rest of the iron to make sure the recipe is right.
Redstone lamps are the simplest output so far, they just turn on when they have signal, emitting light as long as they are active.
Copper bulbs are similar to redstone lamps, but will stay on once activated until they receive another signal to turn off. Less useful as light and more as a redstone "memory" of sorts.
Many other devices can be activated by redstone, here's a short list of the most important:
Well that's the basics of Minecraft's redstone components, thank you for reading and hope this helped you learn the basics and make some cool contraptions.