Hey Guys!
I've just started with electronics and want to make an analogue soil moisture sensor (with Arduino).
When I looked online for an explanation of the working, every site said that it works as a voltage divider.
These are my questions:

1. What exactly is a voltage divider? How does it work (for a beginner) ?
2. The tutorial said that a wire has to be connected from the Vcc to an analogue pin on the Arduino for the readings.
But how can a wire from the Vcc send analogue signals about the soil's resistance? Doesn't it just supply power?
3. The tutorial mentioned a capacitor between the Ground and the signal wire for filtering noise.
What is this noise? How can the capacitor filter it? Why does it need to be filtered?
I've attached an image of a part of the tutorial for reference.
Thanks a lot and apologies for my silly questions (couldn't find a satisfying explanation elsewhere) .

 

A voltage divider is a set of resistors across a voltage supply, at each "Junction" there is a Smaller voltage available, and as you go further down towards ground these voltages get smaller. The amount that they give out depends on the Values of the resistors choosen, its just Ohms Law working out what current is passing through the resistor chain, and then reading off the Voltage across the resistor.

https://www.allaboutcircuits.com/tools/voltage-divider-calculator/

The soil is being used as the Variable resistor ,and it's being pulled up by the 57K, as the soil gets wetter it's resistance will decrease, and as it gets drier, it will increase, so there will be a Variable voltage available at the Arduino input.

In the circuit below, the Total resistance adds up to 24 ohms, so 1Amp flows through all the resistors,. ( This is fine as long as your load doesn't pull the voltage down with its own internal resistance.)