Crosstalk

Definition

When 2 wire segments are in close proximity they interact with each other electrically, this is on account of coupling capacitor between these 2 nets.This Phenomenon is called crosstalk.
This coupling capacitor causes crosstalk delay and crosstalk noise.

Crosstalk Delay:

If there is a significant amount of crosstalk between 2 wire segments and both the nets switch(in the same or opposite) direction simultaneously then it results in crosstalk delay.Crosstalk delay can cause setup and hold violations.
I leave it to the imagintion of the reader to figure out how this happens.

Crosstalk Noise:

If one net is static and a nearby net rapidly switches,owing to coupling capacitance between these 2 wires we will see a glitch on the static net and this is crosstalk noise.