A suspension system is used to connect the un sprung mass of system ( wheel hub ,wheels ) to the sprung mass (all other parts ).
They generally contain a shock absorber and and coil springs.
A shock absorber consist of a Spring and damper. The spring is used to transfer the load or shock gradually form wheels to sprung mass.
The damper is component which is used to dampen out vibrations by converting them to friction energy using fluids.
After seeing the above video , its evident that during shock the fluid is transfered in and out of the two tubes.Then why does a nitrox name sit in there ,lets see
What happens when u shake a Tin can of oil .The oil will foam (aeration ),so the can will be filled with bubbles.
If this is the case ,The same will happen inside a damper ,the fluids continous movement may result in aeration or formation of bubbles .To prevent it the air is evacuated and filled with Nitrogen .
This concept will be explained in the following video
Most commom suspension used in bikes
-A coils over at rear (either monoshock or dual shock)
-Telescopic suspension at front
It may be telescopic (left img) or Inverted fork (right img)
Swing arm suspension
The swing arm suspension is like our hand and elbow joint (fulcrum) this allows the rear frame of bike to move relative to from front frame.
Other aspects :Tires –